Final answer:
A 'Common column' is used in databases to link tables together, often through a primary key-foreign key relationship, ensuring data integrity.
Step-by-step explanation:
The term that refers to a column with equivalent data that exists in two or more tables is known as Common column. When designing relational databases, a common column is used as a way to relate two tables together, usually through a primary key in one table that appears as a foreign key in another table. This is a fundamental concept in the design of relational databases and is crucial for ensuring data integrity and facilitating database operations like joins.