With tutorials, courses and building instructions with gears you could learn how to use Gear Wheels, Warm Gears and Racks. Everything spins. With a few gear wheels you could make it spin faster or harder. Check out the examples of different constructions, robots and attachments that make use of gear wheels.
When you need a LEGO robot attachment to lift heavy things on the competition field. Probably at FIRST LEGO League or World Robotics Olympiad. This attachment uses 4-5 gear wheels to lift a heavy object.
Build with LEGO Mindstorms EV3 parts.
Building instructions for a robot for the World Robotics Olympiad Sputnik competition. This is the light version without the lift at the top.