How to create more than 1 table in Migration?

I followed the guideline here: 

Database Manipulation and Database Forge
https://codeigniter4.github.io/CodeIgnit...forge.html

I managed to run the migration, and successfully created 1 table with necessary fields.
All files are duly placed inside app/Database/Migrations.

So my questions right now are;
1. How to create more than 1 table? (in just 1 Migration file)
2. What is really up() and down() for? (is it a must? can I write a custom method instead?) 

Thank you.


#codeigniter4
#forge
#migration