A riff is a short pattern of notes (usually one or two bars long) which repeats throughout a verse or section of a song. A riff can also be varied to fit a chord progression.
The use of riffs is common in many styles of music including Rock, Metal, Blues, Jazz and Funk. Many of the examples you have already learned are riffs. Here is another example. Learn the riffs in this book and then experiment with them to create your own.
A dot written after a quarter note means that you hold the note for one and a half beats.
A dotted quarter note is often followed by an eighth note.
The following example has a dotted quarter note in the final bar. Take care with the left hand fingering and be patient if you have trouble with it at first. Keep your picking clear and even. This example sounds best with a clean sound and possibly an effect such as chorus.