The only aim in Rust is to survive.  To do this you will need to overcome struggles such as hunger, thirst and cold.
Build a fire.  Build a shelter.  Kill animals for meat.  Protect yourself from other players, and kill them for meat.
Create alliances with other players and form a town.  Whatever it takes to survive.

To play Rust, you will need to install Steam.

Steam is a digital distribution, digital rights management, multiplayer and communications platform developed by Valve Corporation.
It is used to distribute games and related media online, from small independent developers to larger software houses.