It helps to think of it in terms of the etymology. If you're homosexual, you're interested in the same gender, and if you're bisexual, you're interested in both genders, which means if you're asexual, you're interested in neither gender. However, it doesn't mean you're interested in nothing, as that's not necessitated. This confusion is where the terms "libidoist asexual" and "nonlibidoist asexual" come from, the latter being one with absolutely no drive and the former being one where a trigger can pop up in a random place that is itself mutually exclusive from one's experience with human relations.

It's also the hallmark of an asexual if physical experience is not necessary. The norm among humans is that, once a certain age is reached, they become dependent on physical satisfaction. There exists a scale I document though that goes from dependency to feeling averse. This is why it's often stressed it's a spectrum, but the rule of thumb is you are considered asexual if you can pass as perpetually physically satisfied without any work.

Varys person to person, but for me I find that the idea of sex is really hot but the reality is just...not as exciting.