Sexuality is a broad term covering sexual desires (what people find sexually exciting and enjoyable), practices (what people actually do sexually), and identities (how people define themselves sexually).
The word ‘sexuality’ is often used in a more limited way just to refer to sexual identity (sometimes also called ‘orientation’), for example, whether somebody identifies themselves as bisexual, lesbian, gay or heterosexual. Occasionally it is used to mean gender identity. But it should be remembered that there is a lot more to sexuality than a person’s gender or the gender of people they are attracted to. Also, people’s sexual identities often do not neatly map onto their sexual desires and practices, perhaps because they feel pressure to identify in ways that are most acceptable to others. For example, somebody may identify as gay or straight despite having attraction to more than one gender, or have more than one sexual relationship whilst still identifying as monogamous, due to social norms around these aspects of sexuality.