Upon starting term-mode, Emacs delegates all keypresses to the terminal you're running.
That's great for compatibility purposes, but leaves Emacs functionality behind. How do I get back to Emacs features (for example, to switch a buffer).
In term-mode, there are two input modes. In the default input mode -- char-mode -- all keypresses (except C-c) are sent to the terminal to do what it wishes with.
If you change the input mode to line-mode, then regular Emacs commands work. You can switch to line-mode with C-c C-j. You can switch back to char-mode with C-c C-k.