If there's a task occurrence, then there's something you have to do, a.k.a. a task or errand.

用事 generally refers to tasks that you personally need to take care of. Often that means errands like buying groceries or paying bills. It could also mean a doctor's appointment, meeting with a friend, or work tasks like attending a meeting and finishing an assignment. It's anything on your list of things to do!

This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.