It’s a tactic used by people who don’t have the confidence or power in a relationship to communicate directly. It’s usually used to be spiteful, take revenge, or express displeasure, thinly veiled behind some plausible deniability. A passive aggressive action can be something like:

A person preparing food for someone they feel is unappreciative might deliberately over-salt or overcook it to spoil that person’s enjoyment of it

A person who doesn’t like things being left on the floor might purposely step or trip over/kick something they see there, damaging or dirtying it

A person resenting being asked to do a task might make very little effort, do it wrong, or make the situation worse than it was to avoid being asked in the future

It’s essentially a way to be hostile to people you socialize with, but if called on it, the person being passive aggressive can make excuses or deflect blame. It’s not a healthy dynamic and leads to frustration and erosion of trust, and the perpetuation of problems rather than their resolution.