1. What is a relational database management system (RDBMS)?
    A relational database is basically a piece of software that you can modify, access, and process data that is stored in a relational database.

2. What is SQL?
    SQL is a type of language (also the most common way) that allows the user to communicate with the database.

3. What is an ER model?
   An ER model is used to demonstrate the relationship between certain things that are used for organization purposes in a database. 

4. Define the following terms: One-to-one relationship, one-to-many relationship, and many-to-many relationship.
    One-to-one relationship is when one section of a categorical database is related to only one other section. One-to-many relationship implies that one section is related to many other sections that may be in the database. Lastly, a many-to-many relationship depicts the relationship between a number of sections to many other sections.   

5. What is the purpose of a primary key? Why should it be unique?
    The purpose of a primary key is to assign it to certain tables, so the user would be able to access them easily. It should be unique because in that way, it would be easier for the user to do certain commands using the primary key.