Girlish is an umbrella term for any sort of female-aligned, woman-aligned, girl-aligned, or feminine-aligned gender, and it was made as an easy-to-understand alternative to labels such as fingender, fegender, and fiaspec.
Girlish can also be an identity on its own for one who feels like they are sort of a girl, not quite a girl, not fully a girl, almost a girl, a little bit of a girl, or any other sort of variation of that could be described as girlish. The boy version is boyish.