Working with multiple files in vi it’s possible…
:e filename – Edit a file in a new buffer
:bnext (or :bn) – go to next buffer
:bprev (of :bp) – go to previous buffer
:bd – delete a buffer (close a file)
:sp filename – Open a file in a new buffer and split window
ctrl+ws – Split windows
ctrl+ww – switch between windows
ctrl+wq – Quit a window
ctrl+wv – Split windows vertically
hide – close current window
:only – keep only this window open
:ls – show current buffers
:b 2 – open buffer #2 in this window