If you are talking strictly about the rhythm the chords are strummed it is simply the Strumming pattern. A riff can be full chords, single notes back to back, several notes at a time, or any combination of all of those.
What is standard strumming pattern?
A strumming pattern is a preset pattern of down and up strokes played with your fingers or a pick against the strings. The strumming pattern will determine the rhythm for your music. You can strum with either your fingers or with a pick.
How many types of strumming patterns are there?
Applying The Strumming Patterns: You've now got five basic strumming patterns to use. It may take you a while to get them down perfectly, but once you can play these patterns and understand the Constant Strumming Technique, you'll be closer to being able to pick out the strumming patterns in your favorite songs.