Let's consider an example of an Employee table:
Employee (
             Employee ID,
             FullName,
             SSN,
             DeptID
)


1. Primary Key: The primary key is a column that uniquely identifies a record inside the table. Here EmployeeId or SSN can only one primary key.

2. Foreign key: A foreign key is a set of one or more columns in a table that refers to the primary key in another table. Primary key drive foreign key another table. if EployeeId Primary key column is used another table this column will be a foreign key in another table.
. 
3. Super Key: If you add the other column/attribute to a Primary Key then it becomes a super key, like EmployeeID + FullName, maybe a Super Key. 

4. Candidate Key: An individual columns or more separate column inside the table that qualifies for as uniqueness of all the rows. Here in employee table EmployeeID & SSN are Candidate keys. 

5. Composite Key: If a table will have single columns that qualify for a Candidate key, then you have got to pick out a pair of or additional columns to form a row unique. Like if there's no EmployeeID or SSN columns, then you'll be able to create FullName + DateOfBirth as Composite primary Key. But still, there will be a narrow chance of duplicate row.

6. Alternate Key: Candidate column other the primary column, like if EmployeeID is PK then SSN would be the Alternate key