What is Preposition?
1.
A grammar term that you do understand except for it's taboo use at the end of sentences.
It's actually not that taboo.
"Where's my preposition at?"
"I've seen that preposition before."
"What is a preposition atop?"
See
2.
To, from, on, et cetera.
“A preposition is something you shouldn’t end a sentence with.”