Difference Between MS Access MDB and SQL for Mac

I understand that both MDB and SQL are used to mean database. While MDB is a database file that can be opened by MS Access, SQL (Structured Query Language) is a tool in order to properly community the database file.
With this taken into account, I am just wondering on how to MDB and SQL work each other? In what way are they related? In what way are they different? Which of the better and more effective to use in handling database?
Thank you.
