Sometimes a composer or songwriter wants a specific bass note played under a chord. This is indicated by the use of slash chords. The chord name is written first, followed by a backward slash ( / ) and the desired bass note. E.g. the symbol G/B indicates a G chord over a B bass note. This is a first inversion G chord, but if the chord symbol just said G, you would probably play a root position chord instead. In the following example, the slash chords (G/B and C/E) are used as a way of creating a smooth bass line, rather than jumping between the root notes of all the chords.
This piece alternates between the relative keys of C major and A minor. The arpeggio style of playing is particularly effective when playing a Rock ballad.
Slash chords can be used to 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 learnt over various bass notes from the scale of the key you are playing in.
This series of major triads is played over an A bass note, indicated by the use of slash chord symbols. The triads move through all the notes of the A natural minor scale.