what is entity relationship data model?

Answer 1

Data modeling is a conceptual design process that focuses on what data is stored in a database.
An entity is a principal data "object" or element about which data is to be collected. Similar to tables in a relational model.
Entity-Relationship data model is the art of modelling data based on entities and relationships between entities. In most implementations these relationships are simply a binary or recursive mapping between entities.
Object relational mapping is perhaps the widest usage of ER modelling as seen in Doctrine, Eloquent, Hibernate, Django ORM etc.

Answer 2

https://www.javatpoint.com/dbms-er-model-concept