What Ctrl is paste?

Ctrl+V
Windows users: Copy: Ctrl+C. Cut: Ctrl+X. Paste: Ctrl+V.

What is Ctrl B used for?

Alternatively referred to as Control B and C-b, Ctrl+B is a shortcut key most often used to bold and un-bold text. On Apple computers, the shortcut to bold is the Command key+B or Command key+Shift+B keys.