1. What is a relational database management system (RDBMS)?
2. What is SQL?
3. What is an ER MODEL?
4. Define the following terms: One-to-one relationship, one-to-many relationship, and many-to-many relationship.
5. What is the purpose of a primary key? Why should it be unique?

1a. A piece of software that allows you to modify, access and process data stored in a relational database. Relational databases are databases in which data is stored into separate tables with user-defined rules governing the relationship between data ields.
2a. SQL is known as Structured Query Language (SQL). It is the language used to communicate with the database. It is the most common standardized language used to access databases. 
3a. ER model stands for an Entity-Relationship model where it used to define the data elements (entity) and relationship for a specified system and provides a conceptual design for the database.
4a. One-to-one relationship: the relationship between two tables where both the tables should be associated with each other based on only one matching row. For example: One person may only be able to have one thing.
One-to-Many: a relationship between two tables where a row from one table can have multiple matching rows in another table. For example, a book can have multiple authors..
Many-to-Many: a relationship between two entities if for one entity instance there may be multiple elements for the other table. An example would be that a user can checkout many books. A book can be checked out by many users (over time).
5a. The purpose of the primary key is a column in a table which has to contain a unique value which can be used to identify each and every row of a table uniquely. It has to be unique so it can be a unique record such as an id for every set of employees or something of that nature. also, if there is an admin, then there can only be one unique admin or a set of numbers that apply to only admins.