It's used to register all the bot commands placed under /src/commands and has also some utility methods, for example:

• getters for the commands
• a method to check if a message is a command
• a method to reload a command so that you don't need to restart the bot just to change some code in a command file

The CTX (Command context) is a class that's used to store some useful informations about the context of a command, for example:

• the member who ran the command
• the guild in which it was ran
• the channel
• and more...

Every command should have a run method which receives as an argument the CTX.
(You can always replace that with a system of your liking)