Elements of database ER diagram

database er Graph and entity ( Solid type ), attribute , The connection is made up of
The above entity and entity type are two versions found online

1. But after thinking about it, I think entity sets are more suitable for representing rectangular boxes , Because of the Internet er The graph drawing process refers to the entity set , And from the concept of entity set , It represents a set of entities .
2. About the concept of entity , I'm a little confused , It can also be abstract concepts and connections , Is it an entity name
3. I have to er The rectangle of the figure only represents the meaning of the entity name
I don't know your opinions