Sus is an abbreviation for suspended, not sustained, so no, you aren't being told to hold the chord.  There are two commonly used types of suspended chords:

sus4 - A sus4 chord replaces the 3rd scale degree in a chord with the 4th scale degree. So a triad spelled 1,3,5 becomes 1,4,5. the third degree is replaced by the fourth. For example, a DMajor chord,  D,F#,A becomes D,G,A or Dsus4.   The middle note or the third note is raised by a half step. 

sus2 - The sus2 chord follows the pattern 1, TWO, 5, so if in a sus4 chord you play the root, fourth and fifth degrees, for a sus2 chord you play the root, second and fifth degrees.  For example a Dsus2 chord is D,E,A. The middle note is lowered a half step.

That is very often what people mean when they day or write a sus chord, but in practice, alot of players include 3rd in their voicings, usually above the 4. Mark Levine's The Jazz Theory Book ends up defining a sus chord something like,,,a sus chord is a dominant 7 chord where the 4 isn't an "avoid" note.