The OData service defines a structure for every entity set. It also mentions about Datatype for each field. The Entity set is based on tables. This structure is called as entity type in OData service. The Entity types are mentioned in the metadata document.
The metadata document exposes all the metadata of the OData service. It includes Data model, Types, Relations, and semantic information.
The metadata document is viewed through the following URL, which has the addition $metadata at the end of the URL.
http://services.OData.org/v3/OData/OData.svc/$metadata
In addition to the entity types, fields are also mentioned. They are called as properties. The data type and primary key of the table is also mentioned.
