quick question - just want to make sure I'm using the term cis properly... as far as i understand cis is just an abbreviation for cisgendered...which only implies that a persons gender identity, espression, and sexual anatomy all align. it does not also imply the person is straight, does it? ie a person could be cis, but gay, correct??
Almost. Cis people identify with the gender they are assigned as birth- so their internal gender and sexual anatomy match. However, I wouldn't say it has anything to do with gender expression. A man who likes to wear dresses and do feminine things is still a man if he considers himself such. And no it has nothing to do with sexuality. Both cis and trans people can be straight or gay (or multisexual).
Like Fallingdown7 said, it's not about gender expression. It's just when someone's gender identity matches their biological sex at birth- so they're the opposite of trans people. And yeah, cis people can be any sexuality.
Cisgender just refers to a person whose gender identity and sex align and are congruent. Just like with trans people, cis people can be anywhere on the sexuality spectrum.