A "model" is something that represents something complicated and helps people to understand it.

Models can be "3-D models", which are objects that you can touch. For example, some people put together model cars or model trains.

There are also "2-D models", which are illustrations or drawings of something. Texbooks often have models of things, like:

• a model of a cell in a biology textbook
• a model of the inside of a star in an astronomy textbook