The strumming pattern is the movement that you will play on each chords. Depending on the song you will generally play it once or twice per chord.
: you strum with your finger all the 4 strings from the top to the bottom with your index
: you strum with your finger all the 4 strings from the bottom to the top with your index
: you strum the four strings like a but when done you immediately mute the chords with your palm