I dont understand the music scale?

Im learning guitar and I really don't fully understand what a scale is or what its used for. My guess is it a group of notes together and you cant play out side of the group so it makes easier to know the notes. It says a scale is the notes you use to get from to that same note 1 octave higher. But that dosn't expalin how im going to play songs by ear or how its formed. Please explain it to me as simple as possible learning music is complicated.