What is the main purpose of using keys in systems or databases?

The main purpose of using keys in systems or databases is to uniquely identify records and ensure data integrity. Keys allow for quick finding, updating, or deleting specific records without the need to browse the entire table. For example, a primary key guarantees the uniqueness of each row, while foreign keys establish relationships between tables, maintaining data integrity.

Example: In a user database, each user has a unique ID — this is the primary key, which can be used to quickly retrieve information about a specific person.