Rock climbing is just the opposite of rappelling. Broadly speaking is ascending steep rock formations.
There are two forms of this activity namely free climbing and aid climbing. In free climbing one climbs up the rock formation without any assistance of a rope (practiced by professionals) and other one with an aid of a rope that assists in conquering the height.
The key to rock climbing is strength, endurance, and mental control as well as agility and balance. The required pieces of gear are provided by the leader.