Okay, so imagine you have a bunch of different toys that are all very similar but have small differences. For example, you have a big toy car, a small toy car, a blue toy car, a red toy car, and so on. It can get confusing to remember all of the different types of toy cars and which one is which.
Now, imagine if someone came along and said "Hey, let's just pick one toy car to be the main one. We'll call it the 'canonical' toy car. Whenever we refer to a toy car, we'll use the canonical one as the standard and compare other toy cars to it."
The company named Canonical does something similar, but with computer software instead of toys. They create a version of a specific type of computer software, like an operating system or a database software, and call it the canonical version. They make sure that all other versions of that software are based on the canonical version and are compatible with it. This helps people to understand which version of the software is the most important and which ones are just variations.
So, in short, Canonical is a company that creates a standard version of certain computer software to make it easier for people to understand which version is the main one.