It's sometimes necessary to split the view of a file into many windows. Below is a cheatsheet copied from here.
:sp will split the Vim window horizontally. Can be written out entirely as :split .
:vsp will split the Vim window vertically. Can be written out as :vsplit .
Ctrl-w Ctrl-w moves between Vim viewports.
Ctrl-w j moves one viewport down.
Ctrl-w k moves one viewport up.
Ctrl-w h moves one viewport to the left.
Ctrl-w l moves one viewport to the right.
Ctrl-w = tells Vim to resize viewports to be of equal size.
Ctrl-w - reduce active viewport by one line.
Ctrl-w + increase active viewport by one line.
Ctrl-w q will close the active window.
Ctrl-w r will rotate windows to the right.
Ctrl-w R will rotate windows to the left.