What does it mean to have chemistry with someone?

Yes, "chemistry" means you have things in common it doesn't have anything to do with your gender or relationships. so, if someone of your same gender said you have allot of chemistry just means you have a lot in common.

It just means having some sort of connection with someone. Most people associate "having chemistry" with being physically attracted to each other, but you can be attracted to someone for other reasons. Maybe your personalities mesh well, or it can be another factor that bonds you two.

I am straight and that has happened with me I think it's perfectly normal to have a connection with someone of the same sex

'Chemistry'- otherwise known as sexual attraction for one another. Unless you are homo, bi or pan sexual then it is not ok to have 'chemistry' with the opposite sex.