In a CRM context, an "Account" refers to a Company or Contact.
In previous versions of EventPro, Contacts (i.e. individual people) had to be linked to a Company. However, Contacts can now exist independently from Companies in CRM, so the term "Account" refers to any entity with which you interact, whether that is a company, a company contact, or a contact.
Therefore, Account Categories can be applied to both Companies and Contacts.
