This is the 251st most frequent Russian word.
со
"Со" means "with" or "together with."
The word "со" is used as a preposition meaning "from" in this context, signifying motion away from a place.
Мы шли со школы домой.
We were walking home from school.
The word "со" functions as a preposition here meaning "with," indicating accompaniment.
Он поговорил со мной об этом.
He talked with me about this.
Here, "со" is used as a preposition meaning "with" to express the notion of conjunction or time progression.