This symbol is called a quarter rest. It means there is one count of silence. Do not play any notes. Small counting numbers are placed underneath rests. If a rest occurs after you have played a note, you must stop the note sounding. To do this, lift your finger off the fret but keep it lightly touching the string.
In this song, lift your finger off the D note at the start of the second count. This will give you three counts of silence.
Strum Pattern
Strum Pattern
Strum Pattern
Strum Pattern
This is a whole note. It lasts for four counts. There is one whole note in one bar of * time.
Strum Pattern
Strum Pattern