Everything your account comes with is a starting point. You can rename, move or delete Schedules, Types and fields so they match the way your team specifies products. Only account Owners and Super Admins can change classification.
To get there, click the "Account" menu in the bottom left corner, select "Settings", then "Classification" and the "Categories" tab.
Before you delete anything: renaming keeps all the information on your products, but deleting a field erases its information from every product, and deleting a Schedule removes all of its Types. When something is filed in the wrong place, move or rename it instead.
Schedules
Rename or change the code: hover over the Schedule, click the three dots, and choose "Edit". Codes can be up to 3 letters or numbers. Click "Save".
Delete: same menu, choose "Delete". This also removes every Type in the Schedule.
Types
Rename or change the code: click the Schedule, hover over the Type, click the three dots, and choose "Edit".
Move to another Schedule: same menu, choose "Move", pick the new Schedule and click "Move". Its products and fields move with it. If another Type in that Schedule already uses the same code, change the code first. See Moving Existing Types Into Schedules.
Delete: same menu, choose "Delete". The Type is cleared from any products that use it.
Fields
Rename or change a field: hover over the field, click the three dots, and choose "Edit". Renaming keeps the information already entered.
Delete: same menu, choose "Delete". This erases the field's information from every product.
Turn off instead: if you just don't use a field, click its toggle. It disappears from your products without losing anything, and you can turn it back on.
Locked fields: fields with a lock, like Item Code, Model/SKU, Url and Lead Time, can be turned off but not deleted.