What does an it mean to be Jewish?

I found out recently, confirming my suspicions, that I am Jewish by DNA as well as a good amount of family being Jewish by heritage and religion and it was kept from me for my whole life. When I confronted my mom, she said I’m not repeatedly and fought me on it and said that I can’t be Jewish anything because she’s not Jewish by religion, which makes no sense. My uncle is Jewish by religion and has told me that I will always have a home in Israel.

What does this all mean? What does it mean to be Jewish even if not by religion? This has opened a whole new world to me.