The palm branch is a symbol of victory and honour, of triumph over death and spiritual victory. It is a symbol of Christ’s victory of death, associated with Easter (the victorious entrance of Christ into Jerusalem on Palm Sunday).
It has also been adopted into Christian iconography to represent the victory of martyrs (or the victory of the spirit over the flesh).
Since a victory signals the end to a conflict or competition the palm may also represent a symbol a peace (in particular in Islamlic faith, where it is often associated with Paradise).
It may also be found on military graves.