Kowsar means an abundance of goodness and benevolence and a great deal of examples are mentioned in the holy Quran like Pond and stream of Kowsar, intercession, prophecy, wisdom, knowledge, numerous generations, and abundant offspring.
Kowsar is of two instances that one of them is worldly (Fatima PBUH) and the other one is hereafter (Pool of Kowsar).
According to tradition, Pool of Kowsar is a source of sweet water in the paradise that the people of paradise enter it after going through the different stages of judgment day and quench their thirst there.
Two streams are flown from this pond in the paradise and its source is the divine throne.
The pond of kowsar is specifically for the prophet of Islam peace be upon him and the cupbearer of this pond is Imam Ali and other infallible Imams and of course other divine prophets have their own special pond for their followers but they are not as huge and beneficial as the pond of Kowsar.
source : erfan.ir