To me, if I have a romantic attraction to someone, I can see myself being in a relationship with them, while if I have a sexual attraction to someone, I can see myself having sex with them. Obviously both are preferred.
So for example, I am both sexually and romantically attracted to females. I can be in a relationship with a female, develop strong feelings for them, fall in love with them, etc. and I can also feel the desire to sleep with them.
When it comes to males, I only feel a romantic attraction. I can happily enter into a relationship with a male, fall in love with a male, want to spend my life with a male, while feeling no sexual attraction to them.