"silence ability" "silence an area" what these terms mean?

Hello!
New to the game ... I have read some discussions and I have seen some videos on the Web referring to game things like "silence ability" or "silence an area" ... what these mean?
Thanks in advance!
Roberto
New to the game ... I have read some discussions and I have seen some videos on the Web referring to game things like "silence ability" or "silence an area" ... what these mean?
Thanks in advance!
Roberto