Syncopation is the accenting of a normally unaccented beat, e.g., in * time the normal accent is on the first and third beats:
so an example of syncopation could be:
Syncopation is used in all forms of music, e.g., Rock, Jazz, Orchestral, Latin American, etc. Its main advantage is that it can make an otherwise plain beat sound interesting because of the "off beat" rhythm.
An Eighth Note Rest j means silence for the count of half a beat. It can be found anywhere in music and is counted in exactly the same way as an eighth note.