can someone give me a simple definition of each?
The Ordinary Form of the Mass is the current edition of the Missal (the Third Edition of the Missal of Pope Paul VI) that you will see celebrated in the vast majority of Catholic parishes every day throughout the world.
The Extraordinary Form of the Mass (sometimes referred to as the “Tridentine Latin Mass” or “Traditional Latin Mass” or even just the “Latin Mass”) uses the 1962 Missal promulgated by Pope John XXIII.
Extraordinary Form = Traditional Latin Mass- what was celebrated in the Roman Rite from 1570 to the late 1960’s
Ordinary Form (sometimes erroneously and condescendingly referred to as “Novus Ordo” or “New Mass”) - the Mass that is celebrated in the vernacular (it can be in Latin, but not to be confused with the EF though). The Mass that you are probably attending in your local diocese.