Guitar basics: Pull-offs
You can change between two notes by picking them separately, but if the first note is higher than the second in pitch, you can play what's called a pull-off.
A pull-off will make the transition between two notes smoother, which will make your playing sound more fluent.
This video lesson shows you how to perform pull-offs correctly and provides you with two examples to try for yourself.
These examples come with free tab.