How to Strum Guitar
When you brush your fingers over the strings of guitar it is called strumming. Upstroke is the act of strumming the guitar from down to up while downstroke means the otherwise - from up to down.
When you strum, you may either use plectrum(pick), thumb, or other fingers though others prefer to use the guitar pick to avoid hurting their fingernails especially when there's a need to strum harder. Classical guitar players mostly use thumbs to give off smooth strum and often combined with finger plucking.
Sometimes you may wonder why a certain song has only two chords but it sounds as if there are too many. The answer is due to strumming. A combination of finger movement and a good strum pattern makes it easy for you to do the same.