There are the following four components in the ER diagram:

Rectangular box: it represents an entity, and the entity name is recorded in the box.

diamond box: indicates contact, and the contact name is recorded in the box.

oval box: indicates the attribute of an entity or contact, and records the attribute name in the box. For the primary attribute name, underline it.

according to the main example, the ER diagram is as follows for your reference:

ER diagram.