"Kye, what the heck is the difference between a scale and a key and a mode?"
I'm so glad you asked!
Scales are made up of a collection of notes. Kind of like a painter's pallet.
Those notes--also known as steps or semitones--are found by a pattern of half and whole steps. That pattern is the scale. Where it starts from is the mode of that scale. So D Major is a mode of the Major scale starting on D. Same pattern!
I don't know what a key is, but it's probably another word for mode.