"Whatevs" is a shrug turned into a word. Someone tells you something, and you reply "whatevs" to show it does not bother you, you are not going to argue, and honestly you are not that interested. It is the short, playful form of "whatever", which does the same job. That tone matters. Depending on how you say it, it lands anywhere between light and rude. Said warmly, it means "I don't mind either way, it's fine". Said flatly, it means "I've stopped caring about this conversation" — and that can hurt, especially if the other person is being serious or apologising. Teenagers are famous for using it on parents, and parents are famous for hating it. It is young, casual, and mostly spoken or typed to friends. "Whatevs" sounds even more offhand and jokey than "whatever" — the clipping makes it lighter, which can soften it, but it can also make you sound like you cannot be bothered to finish the word. It also shows up occasionally standing in for "whatever" in the sense of "anything": "order pizza, noodles, whatevs".