I'm learning English and would like to know what this expression actually means?

Thank you! :)

Pet peeve means it's something that irritates you, makes you angry/ annoyed.
My pet peeve is people who interrupt. I hate people who interrupt someone when they're talking. They need to learn manners and wit their turn. Anyway... hope that helped you. Bye.

Something that pissed you off. Whatever makes you mad or annoys you. Man I sure have a lot of those :D -Spidey

The phrase "pet peeve" comes from the word "peeve", meaning something particularly irratating or annoying. The first printed usage of "pet peeve" was in 1911 so the use of the phrase is fairly recent considering language history. When you have a pet peeve you have a very favorite irration to complain about. We all have at least one pet peeve, some of us have more. Lol.