Asexual is when somebody isn't sexually attracted to someone.

Aromantic is when somebody isn't romantically attracted to somebody. 

There are umbrella terms to these two terms. There's demisexual, grey asexual, and a whole other list.

Some people are both which is called Aro-Ace. 

Asexual flag: Black, grey, white, purple

Aromantic flag: Dark green, light green, white, grey, black