How do you open a new file in a vertical split?
:vsplit filename
Use :vsplit filename or :vsp filename to open a file in a new vertical split to the left of the current window.
Tag: open
How do you open a new file in a horizontal split?
:split filename
Use :split filename or :sp filename to open a file in a new horizontal split.
How do you open a new tab in Vim?
:tabnew
Use :tabnew to open a new empty tab, or :tabnew filename to open a file in a new tab.