Gender expression is any and all mannerisms, personal traits, etc. which serve to communicate a person's identity as they relate to gender and gender roles. masculine, feminine, and androgynous gender expressions can be present in people of any gender or gender expression- even though they are often associated with men,women, and non-binary genders respectively.
Neutrois or agender people may wish to have no gender expression at all, which many find difficult to achieve in our gendered society.