Link has two different types of collisions:
When Link moves, a vector is drawn from link's current position to what a theoretical final position would be. If a wall is in the way of the small collision, Link will travel in that direction and stop at the wall on the next frame. If a wall is not on the way, then Link will tavel the full distance. However, there is another collision check: Link's big collision is checked after the small collision. It pushes Link back 35 units away from the wall he was pressed up against. This normally prevents Link from fitting through tiny cracks in walls.
However, if a small gap exists in a wall, and if Link can travel through it without either collision colliding with the wall, then you can clip through it. Thus, as long as Link's small collision passes clean through the gap, and as long as the big collision can completely pass the wall in a single frame, Link will not be stopped by the wall. Since Link's big collision radius has a 35 unit radius, clipping through a misaligned corner in this way requires at the very least 35 speed, but it can require more speed in some circumstances (if you can't stand directly against the corner for example). This speed is not normally reachable without glitches (like superswimming or enemy sliding).
But Link can use bombs to get displaced by more than 35 units in one frame. To do so, pull a bomb then press B to drop the bomb behind Link. The displacement from this action is usually enough to fit Link through gaps in corners. These gaps either exist because the walls are misaligned, or because of rounding errors. This technique is known as Bomb Push Clipping. Note that dropping a bomb this way requires a sword. In theory, this technique can be done in many other ways (you could get the displacement by dropping a pot instead of bombs, or by running into bombs if you don't have a sword). But the bomb method is generally preferred.
Bomb Push Clips can be used to clip through corners in various places. Here are several useful bomb push clips.