Thank you for the opportunity to help you with your question!
Nosotras is a term meaning "we" or "us." It is used when talking about a group of which the speaker is a part. The gender differences are "nosotros" for the masculine and "nosotras" for the feminine. The feminine use is applicable when the entire group is female.
Please let me know if you need any clarification. I'm always happy to answer your questions.