Operate provides two ways to categorize Accounts:
The Account 'Record Types' which define how your Accounts are being managed by the system. These can be for example: Account, Prospect, Broker, etc. Read more about customizing Record Types.
The 'Account Type' is a dropdown field that can be added to your Account pages. You may want to use this for more detailed Account categorization, depending on your business practices, which you may use for reporting purposes, for instance.