Apical Dominance. That's a term you should become familiar with and understand somewhat if you're gonna be doing any pruning. Unfortunately, when it's explained in most texts, it's not explained in easy-to-understand terms, and not even fully understood by science, just like they can't explain why some people intentionally walk around with their pants falling down. This particular phenomenon doesn't blend especially well with pruning, even more especially if you're doing it in a ladder.
What the term "apical dominance" means, as well as I understand and can explain it, is that the terminal bud tip of a trunk or any given parent branch, at least a more vertical branch, tends to have much more vigor than any later/side branches or buds waiting to become branches closer to or further down the trunk. The terminal bud is King. At least until it sprouts and a new one takes over, or it gets knocked off. With all this hereditary monarchy, No wonder the British like trees so much.
The apical bud, otherwise known as the terminal bud, or tip of the tree or tip of the branch, mysteriously maintains superiority over all other branches and buds lower down the line with a hormone called auxin. This is the phenomenon that's not fully understood and it may work by means of several different mechanisms. Terminal buds are like Mr. Potter or some Republicans, who want most of the power and go out of their way to take away the well-being of those below them.
Trees tend to grow tall and have long branches due to this mechanism. They're more likely to reach the sunlight if they're they're tall while being in competition with other trees. You might liken this to how humans became dominant primarily because they became taller and more manipulative of their surroundings.
If you cut the terminal bud or the last few inches off a branch, the remaining buds go nuts, trying to take over, much like when a dictatorship is overthrown. The one closest to the new gmailend tends to take over, but other buds gain some vigor to a lesser degree, at least until the new tip gains momentum.
To maintain the approximate same natural shape as before pruning but in a more compact fashion and with more tapering branches, you want to cut just above a bud that's pointing in the preferred direction, and not at a sharp angle. There is a tendency if you cut above a bud and not above an actual already-existing lateral/substitute branch, that the bud will generally grow fairly straight and follow the footsteps of the tip that was removed, within, say 10 degrees. You usually want this new replacement branch to point outwards, maybe up just a bit, or down a bit in some cases. Some expert may take me to task a bit on this point.
Severe pruning may ruin this natural structure, at least in the short term, and can create more of a bush, lollipop, mushroom, hedge, whatever you want to call it. It's generally not what you want in a natural-looking tree. You should strive for a stronger, but generally the same-shape tree as the Good Lord intended in the best specimens. Of course we manipulate some species to look a certain way while still appearing to be natural. Kinda how Bruce/Kaitlin Jenner does a pretty good job of approximating the look of a natural woman, with the goal that people couldn't tell what the real story is unless they read tabloids.
For a fun little analogy, let's think of it this way. Suppose you have a garden hose hooked up to a spigot. The terminal bud would be like the end of the hose, with a sprayer attached. The rest of the hose would have pin holes every few inches, back to where it meets the spigot. If you open up the sprayer fully, almost all the water would come out the end. If you open up the sprayer about half way but maintain the same pressure from the spigot, most of the water would come out the end, but some would come out of the pin holes. More water would come out of the holes near the end. If you shut the sprayer off altogether, the holes would tend to more evenly distribute the water because the pressure isn't focused at the end. Now, think of removal of the terminal bud as the sprayer you shut off, and poking an even bigger hole in the furthermost remaining pinhole is like the new replacement terminal bud. Most of the pressure will come out of that new dominant hole, but some will be diverted to the remaining holes, though not a lot. If you were to somehow be able to immediately put the sprayer over that new, bigger hole, and turn down the pressure of the sprayer very slightly, you can see where this is going.
The side branching tends to be longer further back coming out of a parent branch, because it's had more time to grow. But as the parent branch lengthens, the vigor of these side branches lessens, and eventually will cease growing or even die, leaving the outermost side branches with the most vigor. Cutting the patent branch back closer to the lateral branches increases their vigor. Any side branching contributes to the bulk of the patent branch, increasing diameter and increasing tapering as long as there's some side branching nearest the base of the parent branch. Concentrating all the growth near the very tip of a parent branch will create a weak branch with little tapering. Most conifers don't ready tolerate pruning into a parent branch unless there's still fresh foliage behind it. If all the energy is concentrated at the end and you cut it off, say bye bye to the whole branch.
When people do pollarding, liontailing, topping, etc., they tend to reduce or completely remove branches closer to the trunk and concentrate the energy into the very tips of the branches, and cut the end off too. This is not a good idea and it's just busy work that will lead to repetitive, unproductive annual pruning and in some species, a whole lot of mess coming out the end of a branch and an ugly knuckle. In fact, people sometimes top their trees in an effort to make the tree more compact, but the effect may be exactly the opposite in time. This is exactly what people compulsively do with Mulberry trees, which look absolutely terrible for half the year, especially winter, and Crape myrtles, hence the term "Crape Murder".
Pruning that's too severe will frequently cause vertical water spouts/sprouts to form, as the tree reacts to pruning, trying to replace what it lost, sometimes with more vigor than before. In actuality, there's the same amount of roots as before pruning with energy that has to go somewhere. During summer pruning, it's more of a two-wayvstreet as the leaves are providing the roots with energy, and removing some of the foliage slows down the tree's growth. Water spouts/sprouts never look good, and my take on it is that you might leave them for a short time lower down the branch to increase tapering, remove the ones nearest the tip right away, but remove all or at least redirect into a pleasant direction before they become thicker than a pencil and would leave scarring that wouldn't seal (not heal, exactly) over relatively quickly. Water spouts/sprouts tend to occur a lot more on certain trees than others. If you look around, you're likely to see some vertical branches in a lot of trees that don't look right, especially if the tree has a more horizontal branching pattern. Water spouts/sprouts are much more likely to exist with infrequent, severe pruning, than frequent, minor pruning. It would be like eating well and taking care of your skin over a long period of time, where you can be healthy and look good, instead of going on a crash diet and getting botox, where things just aren't the same. Interestingly, apical dominance is less pronounced on more horizontal branches than on more vertical branches since gravity helps the auxin move down and stores growth in lower lateral buds and branches As a result, horizontal branches tend to have more sprouts along the length without pruning, and when pruning is carried out, especially excessively, more water spouts/sprouts. It may also explain why more vertical branches tend to have less taper and grow faster in length, and aren't as strong for those reasons, along with the fact that the low angle of departure from the trunk makes for a better chance of splitting like firewood with an axe and ruining your day.
I hope this explains things a bit, and gives you a better understanding of why pruning should be done properly, and what the results will be. Please try to understand the consequences of every cut you make. And stay away from the botox.