A Suspended Chord is one in which all 3^rds are replaced with either 2^nds or 4^ths. Losing the 3^rd can make a chord sound very vague or open, but the addition of the 2^nd or 4^th will certainly make up for that loss of character.
Despite losing a note from our Maj or Min triad these still qualify as chords because of the additional 2^nd or 4^th. Remember, a chord is a collection of any three different notes, usually these happen to be a triad, but not always.

Here are some common uses for Sus Chords:
It’s quite common to set-up chords in longer sequences. This is usually done by playing either the root note of the chord to come, or it’s 7^th, within a preceding chord. Sus chords can allow us to do this.
If you’re spending a lot of time on one chord, you could vamp a little, or play a short melody using the 2^nd, 3^rd and 4^th whilst still playing the rest of the chord.
Sus chords can also be a neat alternative to Extended Chords when you’re looking to create a chord sequence with common tones, or maybe just something a little different.
If a minor chord sounds too dark, or a major chord too bright, then try replacing them with a Sus Chord.
They sound cool.

Below are some of the easiest Sus chords to play in the open position, along with Barre Chord diagrams for roots on the E and A strings.
In these charts Sus2’s are coloured Orange, while Sus4’s are Yellow.