remap is an option that makes mappings work recursively. By default it is on and I'd recommend you leave it that way. The rest are mapping commands , described below:
:noremap are recursive and non-recursive versions of the various mapping commands. What that means is that if you do:
:map j gg :map Q j :noremap W j
j will be mapped to
Q will also be mapped to
j will be expanded for the recursive mapping.
W will be mapped to
j (and not to
j will not be expanded for the non-recursive mapping.
Now remember that Vim is a modal editor. It has a normal mode, visual mode and other modes.
For each of these sets of mappings, there is a mapping that works in normal, visual, select and operator modes (
:noremap), one that works in normal mode (
:nnoremap), one in visual mode (
:vnoremap) and so on.
For more guidance on this, see:
:help :map :help :noremap :help recursive_mapping :help :map-modes