Basics of oData
What is oData? It is a standardized protocol based on REST & HTTP protocols that supports basic CRUDQ [CRETAE, READ,UPDATE,DELETE,QUERY] operations by creating and consuming APIs.
The entity data model contains entity type(s), entity set and the association etc.
The entity type is noting but collection of different fields of an object like sales order,purchase order, customer, vendor or product. A key is defined in an entity type to unique identify an entity like sales order number, customer number etc.
An entity set is a collection of entity types.
In a data model, more than one entity type can be defined and the relationship between two entity types is called their association .