Reward is a translation of Hasanah حَسَنَة which is the reward granted by Allah to pious on doing good deed. The size and amount of the reward is very great which can be more than all the bounties of this world. Every good deed will make you gain ten times the reward of it as Allah says in Quran (Sura 6, verse 160).
Reciting every letter in Quran will bring ten rewards as it is mentioned in authentic Hadeeth. (al-Kaafi 2:448).