whats the difference between OVA and the 아니메 aired?

Well, 당신 probably already know what the definition of an OVA is, but it can be multiple things:
- A side story of an anime
- A prequel 또는 sequel of an 아니메
- A short story almost completely disconnected from the 아니메 itself
- Fanservice
- An 아니메 series that simply didn't air on television, but stands on its own

If I like an anime, I'll usually check out its OVA if it has one. I will warn 당신 though, if 당신 watch the OVA's for every 아니메 당신 watch, 당신 will eventually encounter some major wastes of time. It all depends on the show, though.