nmapmeans “map a key sequence when in normal mode” (see vim’s docs).<silent>tells vim to show no message when this key sequence is used.<leader>means the key sequence starts with the character assigned to variablemapleader— a backslash, if nolet mapleader =statement has executed yet at the pointnmapexecutes.
And the v is the rest of the key sequence.
So overall this is mapping, in normal mode, a backslash-v key sequence to show no message and execute :EditConfig which is likely a function defined previously in the vimrc to edit configuration files (see for example this vimrc, search in browser for editconfig). :call EditConfig() at the end (as the vimrc file I gave the URL to uses) would be better, I believe.