LineNumbers

See here

Line numbering

" on
:set number
:set nu
" off
:set nonumber
:set nonu
" toggle
:set number!
:set nu!

Relative numbering

" turn relative line numbers on
:set relativenumber
:set rnu

" turn relative line numbers off
:set norelativenumber
:set nornu

" toggle relative line numbers
:set relativenumber!
:set rnu!

Highlight current line

:set cursorline

also

:set cursorcolumn

Styling:

:hi CursorLine   cterm=NONE ctermbg=darkred ctermfg=white guibg=darkred guifg=white
:hi CursorColumn cterm=NONE ctermbg=darkred ctermfg=white guibg=darkred guifg=white