In the winter they built high wooden ramps and covered them with water, which became ice. The ramps were about two feet wide. Passengers go to the top of the hill and would sit in a sled and would slide down the hill and onto a straight away. In summer the sled would run on wheels. This is how roller coasters started.
Roller coasters come in many different styles.
Steel coasters can be looping, non-looping, suspended, and stand up. Wooden coasters can be twister and out and back. They can be regular, too. If you want to know what these words mean look in the glossary. One of the best roller coasters is the Beast.