Well, our next area of discovery in our Explorer learning path is going to be on relational database management system concepts.Which takes us to, then, the definition of a relational database.From that entity model here, then, in turn, it allows us to logically generate or create, then, the table instance charts, and thereby allowing us here to create tables on disk.So a foreign key in the employee table will allow me here to relate these two tables to each other by virtue of listing then a foreign key column in the employee's table that correlates over to a primary key column in the departments table.That takes us here to 2, and, of course, we'll perform a demonstration on relating multiple tables by using Oracle SQL developer.And if you have synonyms for it here, they're placed next to the entity singularly named, but enclosed in parentheses, as we illustrate here in this case of the employee and the department.And it is a collection of relations or two dimensional tables controlled by server processes.So first and foremost, the entity is an aspect of something significant or important within the enterprise.And finally, of course, and the whole purpose of a relational database is the fact that this information, because it only contains information about, say, employees, and the other table only about departments, we should be able to then, in turn, uniquely, right here, identify those employees.In working with this one, we need to understand here that an entity or relationship model is an illustration of the various businesses and relationships that we need here to meet the business needs.That takes us over to the modeling conventions here that we need to understand concerning the ERD.I consider it here in English, right here, the attribute here is the adjective that helps describe the noun, which would be the entity.If it's the primary, a unique identifier here, it's denoted here with the hashtag.A secondary one, if there is one here, is going to be hashtag, but also, again, enclosed in parentheses.What we want to be able to do, of course, is to relate these two tables to each other using, of course, these primary keys, and then establishing a relationship, utilizing here, our foreign keys.Objectives on this one is to describe the RDBMS concepts.It's always singular in name.