For your Electric gutiar. For example my Gibson les paul Studio has a 5 knobs. Well one is leaver. the leaver looking thing will choose what kind of pick it will you use. If you have th eknob in first postion its called a harsh pick up and mostly used for playing leads. As you move away it gets deeper. Soem gutiars come wiht 4 other knobs. You move it to make it deeper. And one or 2 are for the voulume.
Now for the amp it deeps. Gain is for distrition and well i am not going to get into that.