I have always been confused on whether sexuality is attraction to a specific sex or a specific gender?

Sexuality is both. Sex and gender are essentially the same thing, but sometimes gender can mean that the person is transgender. Sex refers to the person's genitals.

Gender and sex get confused a lot. Sex, there's only two, male and female (don't freak out when I say that) because sex defines what reproductive organs you have. Gender, there's multiple. Usually, people are attracted to a sex, not a gender, but if you don't care what the person your dating's sex is, then it's attraction to a gender. I hope that cleared it up :)

For some, it's based on sex. For others, it's gender. There's nothing wrong with having those kinds of boundaries in place. When you add trans people, like myself, into the mix, terminology can get confusing, but all you have to do is ask! I'm a gay trans man and date other cis or trans men, but I know many trans men who still think of themselves as lesbians for being attracted to women. There's nothing wrong with navigating the world with the terms and experiences available to you.

Sexuality is complicated. Sexuality exists on a spectrum and is not binary. Binary means that you place yourself in one category or another. Sexuality is something you discover over time, but attraction is something that can be person to person, gender specific or a specific sex. All people are different and have different desires and preferences. If you find yourself trying to place yourself in a category, it may be difficult. However, some people do have clearly defined characteristics they find attractive. There is no rule of thumb, but as long as you are respectful of others and open to your own emotions or attractions, you should be on the right track.