I've known some people who identify as asexual and they're far from a monolithic group.
Some asexuals have sexual thoughts, desires, feelings, etc., but don't feel the need to fulfill them by having sex with anyone.
If you're a straight guy, then you probably don't have any desire to pursue sex with another guy. An asexual person can have a normal sex drive in the same way, but not have the desire to have sex with either gender.
A male friend of mine figured he was asexual in his early 20s when he tried having sex and each time he just wasn't into it. Normal sex drive but just a general lack of sexual desire for other people.
It's a complex topic and hard to put everyone in a perfect box of what they are.