Gender identity
Gender expression (also called, "gender presentation") means how a person dresses, looks, and acts, in ways that might affect how other people view their gender. Someone who wears men's clothes and acts in a masculine way has a male gender expression.  Someone who wears women's clothes and acts in a feminine way has a female gender expression. This is different from gender identity because people can choose to look or behave one way even if that is not how they feel inside. Sometimes people call this gender presentation or just presentation.