The accounts represent a company in a CRM.

The contacts represent an existing point of contact at a company in a CRM.

The engagements represent an interaction noted in a CRM.

The notes represent a note on another object in a CRM.

The opportunities represent an opportunity in a CRM.

The tasks represent a task in a CRM.

The users represent a user in a CRM.

The fields of entities in a CRM.

Accounts represent the companies or organizations that you are in contact with. Accounts have one or more Contacts associated with them.

Tickets can be grouped into Collections. Collection resource usually maps to the various grouping systems used in the underlying product. Some examples are lists, projects, epics, etc. You can differentiate between these grouping systems using the type attribute of a Collection.

Core resource which represents some work that needs to be carried out. Tickets are usually mapped to issues, tasks, work items, etc. depending on the underlying product.

Fields represent the attributes defined for various entities in the underlying product. Depending on the underlying product, custom attributes can be defined by a User on various entities like Ticket, Contact, etc. is_user_defined attribute within Field can be used to differentiate between custom and system defined Fields.

Users represent the people using the underlying ticketing system. They are usually called agents, team members, admins, etc.

Workspaces represent the top-level subdivision in a ticketing system. They usually have their own set of settings, tickets, statuses, priorities and users. Some of the usual terminologies used by the products for the top-level subdivision are projects, bases, spaces, workspace, etc. A Workspace could belong to an Organization.