CommandContext

The CommandContext is a class used in the run method of the commands to include all the properties you need, it also includes a lot of getters and useful methods to shorten your code.

// from a command
async run(ctx) {
    ctx.send(`${ctx.commandName} executed by ${ctx.user} in ${ctx.channel} !`);
    ctx.react('👍');
    ctx.send('I will now destroy your message in 10 seconds...');
    ctx.deleteMessage(10000);
}

SubCommandContext

From within SubCommands the ctx argument in the callback is an instance of the SubCommandContext class which includes some other fields related to the SubCommand itself.

Documentation