title: Why some commands in vim require a colon while some don't?
body: <p>Some of the commands in vim are given by first typing a colon (:) eg . :wq for saving a file and quitting . While some of the commands don't require a colon for example the Replace command (R). I want to know what is the difference between the two approaches ? Is there any specific rule as to which ones require a colon and which ones don't ?</p>