Specifically, I am referring to javax.persistence.Entity.
Based on the documentation it shows when I hover the mouse over, in VS Code it states that:
Specifies that the class is an entity. This annotation is applied to the entity class.
What does it mean for Spring JPA that a class is an Entity?
A class of type Entity indicates a class that, at an abstract level, is correlated with a table in the database.
Each object instantiated by this class indicates a tuple of the table itself, containing the information of the latter.
I recommend that you find out about what object relational mapping is.
I also recommend this page that talks about ORM in Spring.