If you need to add a description to a Category to give some background or explanation for the products within the category then this is where you can do it.
Login to your Stor Shop here.
Open the Categories menu on the left side menu
Select the relevant Category and select Edit
Scroll down to the Details area and enter whatever you need to in the Description text area:
Hit Save and you're good to go.
Note: Make sure you Show the Category Description in the Category Page Config in the Content builder.