A SuS chord, short for "Suspended" chord, is a chord where the major 3rd of the chord is replaced with the 2nd or 4th degree of the scale. For example, the C major chord consists of the notes "C-E-G". To form a suspended 4th chord, you will replace the "E" note with the "F". Now you have "C-F-G".
To form the suspended 2 chord, you would play a chord consisting of the notes "C-D-G" The sound of a Sus chord sounds unresolved and is very useful when you have to play a major chord for an extended amount of time.
Below are examples of how to implement the Sus2 and sus4 chords in a musical phrase. The first example starts in the key of C and later modulates to the key of D. The second example simply uses the chords Csus2, Fsus2, and Gsus2.