There are many resources covering the differences between sex, gender and sexuality (you can start with Minus18’s article).

In brief, our sex is our physical body: what genitals we have or levels of particular hormones. Generally, when we’re born a doctor will write a sex on our birth certificate based on their assessment of these physical characteristics.

Gender identity on the other hand, is our sense of self as it relates to being masculine or feminine. Basically, it’s how we feel in our mind. For a lot of people, gender identity will match their assigned sex at birth. This is called being cisgender or cis. When our gender identity doesn’t match the sex we were assigned at birth, this is called being transgender or trans (e.g. being assigned male at birth, but identifying as female).

Some people identify with aspects of male and female while others might not really feel like either. This is called being gender diverse, gender non-conforming or non-binary.

For gender diverse people, the word they use to describe their identity is very personal and entirely up to them. Some gender diverse people might start using different pronouns (which are words like ‘he’, ‘she’, ‘they’ etc).