A canyon is a deep gorge, typically one with a river flowing through it, like the ones found in North America.

Canyons are formed by erosion from rivers over many years. They start as just rivers, but over time the rivers wash away the rock under them, and eventually they get deep enough that they become canyons.

A famous canyon you can visit is the Grand Canyon, in Arizona.

A ridge is a long narrow hill top, mountain range, or watershed.

They are usually formed by tectonic plates that push together or erupting volcanoes. There can be underwater ridges.

You can visit the Hornli Ridge in the Matterhorn Mountains in Switzerland.

A gorge is a narrow valley between hills or mountains. They usually have very steep rocky walls and sometimes streams running through them.

They are eroded by streams that run through the mountains or hills. Most of the time those streams are started by major flooding.