Upgrading from 3.7 to 4.1 - Category Field Question

[Alex]

Hi, 

According to https://dotcms.com/docs/latest/upgrading-to-dotcms-4-0#ContentChanges,

The Category Tab Content Type field

• If you have any Content Types with a Category Tab field, you must remove this field from the Content Type beforeupgrading to dotCMS 4.0.

My question is a "Category TAB field" is a standard Category Field?  Or, is it something that it was called from the legacy of 1.9?

If it is then a category field, does it mean that I have to delete all those fields in the content types and then upgrade and recreate those categories?

Sorry it is a bit confusing.

Thanks,

Alex