In the following example, you will notice some new chord symbols. These symbol indicate a chord with a specific bass note under it, and are called slash chords. For example, in bar 2, the chord symbol G/B occurs. This indicates a G chord played over a B bass note. In bar 4, the symbol G/D indicates a G chord over a D bass note. In bar 5, the symbol Am/E indicates an A minor chord with an E bass note. Slash chords are often used to create smooth, melodic bass lines and the symbols tell you that a note other than the root is played as the bass note of the chord.
The following example demonstrates the progression from the previous example played fingerstyle. As well as the slash chords, notice also the use of bass runs to connect the chords. The extra bass notes here all come from the A natural minor scale. Experiment with other ways of strumming and picking this progression.
Slash chords can create many different harmonic effects. Each combination has a specific name and often creates an entirely new chord. Basically you can play any chord over any bass note as long as it sounds good. Experiment with playing all the chords you have learned over various bass notes from the scale of the key you are playing in.