The FERMATA is a symbol that looks like this, and you use it to stop the time. In music you need time, you have to play on time "A tempo" all the time, but sometimes you need to give a little pause to the music, that's when you use the FERMATA. The best example is in "Happy Birthday" when the sing "...happy birthday dear Charly...." and the make a pause or stop for a little bit, then they finish the song "a tempo" "....happy birthday to you"