What does it mean when a guy competes for your attention?

[VenusxoxAphrodite]

This guy has a girlfriend yet the other day he was competing with this guy for my attention.
I was having a conversation with another guy. And he came up to us and interrupted our conversation.

I did have sex with the guy once who interrupted our conversation. And I have shown him a lot of attention throughout the years.

[Helotome]

No no if he had a girlfriend but getting jealous with you? That's crazy. Why care if he got another person? As long he ain't doing something other than interrupting then ignore his ass