Bonus: Why Zotero?
With so many reference manager software, why use Zotero?
Transferability. It is an open source package that I download and keep. No matter what school I move to, I can access and use my zotero.
Always Free. No paywall. You can pay to get a larger online storage thing, but there is also open source code to do this for free.
Great support community. The open-source nature of Zotero means that there are highly motivated individuals solving the problems that you are having.
Widespread usage. Though not everyone uses Zotero, a lot of people do. You can easily export your file structures to them, and also export your files to other software like endnote. You can even publish online folders that many zotero users can add and access.
Word Plugin. I can cite as I write in word.
Memos. The memos in Zotero are excellent. You can copy and paste text from a PDF open into zotero straight into a memo and it will auto quote and cite for you.