A bomb jump enables Link to cross short gaps by taking damage from a bomb, pushing Link over the gap.
How to perform it
Different types of bomb jumps requires different techniques.
The simplest form of a bomb jump is getting across a two-tile gap (or less) in a cardinal direction. There's generally two methods for this trick:
Link needs to be placed one or two pixels away form the gap, with a bomb going off on the opposite side of the gap.
Link can be up to six pixels from the gap if the bomb goes off during a bonk animation.
Note that when using the bonk method, you will lose some frames due to a) Link usually being placed farer from the gap, making him also land closer to the gap on the other side, and b) the bomb won't hit Link until he has landed completely from the bonk, so depending on when you start the bonk you will lose a variable amount of frames.