What is the primary function of "Field” in Data Service Entities?

The fields of an entity are used to define the attributes and relationships of the entity, such as the name, type, format, and validation rules of each field. The fields can be of different types, such as text, number, date-time, relationship, auto-number, choice set, and file. The fields can also be customized and modified according to the business needs.

References: Data Service - Entity Field Types, Data Service - Customizing an Entity