This page show strummings for guitar (or Ukulele). Each image shows a different way to play. The rhythm is written by the notes written, and the strumming is determined by the arrows above. This photo is playing from Top to Bottom. And this image: is playing from Bottom to Top.
Many songs have many strummings that can fit according the rhyme, since the accompanying musical instrument does not play a particular strumming. For example, a song played in Arpeggio - a broken chord or a song accompanied by a piano.