up is a preposition or an adverb. It means arriba, hacia arriba. It's the opposite of down, abajo, hacia abajo.
I met an interesting beggar up the road.
Please, turn up the amplifier a bit. I almost can't hear the music. /Subir el volumen./
It also combines with many other words. Example:
Maggie Sloane lives upstairs from Carolyn Duval. (Preposition.)
My friend lives uptown. (Upper /superior, más alta / or northern area of a city.)