A lawnmower is a tool for cutting the grass in your lawn. Lawnmowers come in several different types.

Lawnmowers can be ride-on like a small car, and you drive them around over your lawn. This kind is good for really, really big lawns.

Then there are push-mowers that don't have an engine and rely on you pushing them to spin a blade that cuts the grass. This kind are hard to use and are not very common anymore.

The most common is the kind in the picture, where you push it to make it go where you want, but the blade is powered by a petrol or electric motor.