Put simply, a zugzwang is when a player has to move but doesn't want to because doing so will worsen their position.
Please take a look at the following position.
It is black to move, but notice that black has no legal moves other than with the cannon and the chariot. Moreover, the cannon is pinned to the general by the red chariot, and so it can only move along the same file (vertically). Similarly, although the chariot can technically move vertically, the red chariot can then just move away, resulting in a discovered check by the cannon, which also happens to be checkmate:
Therefore, the only reasonable move is to take red's cannon with the black chariot, but obviously this is a sacrifice black would rather not make, hence the zugzwang.
Here, it is again black to move, but this time things are even more forcing. The only piece that can move is the black cannon in the vertical direction. Thus black is forced to give up the cannon as well, hence the zugzwang.
Notice, that instead of capturing the cannon like I did in the game, I could've moved my chariot to block the cannon so that the following stalemate arises, winning the game for red:
