The Dawes Severalty Act was a law passed in 1887. Its purpose was to try to assimilate Native Americans and to encourage them to live more like white people. It can also be argued that a purpose of the law was to make it easier to take reservation lands away from the Native Americans.
The Dawes Act took the land that had been given to Indian tribes and split it up between the individual members of the tribes. The tribes were no longer allowed to own the land communally. This was meant to push individual Indians to own their own land and become farmers. However, all the land that was not parcelled out to individual Indians (160 acres per head of household) was sold to white settlers and to railroad companies. This meant that much more of what had been Indian land was available for white use.
In this way, the Dawes Act had two goals. It was meant to "civilize" the Indians, but it was also meant to make it easier for white Americans to get the Indians' land.