"MÁS"(it is an adverb) means "MORE"
-I need more... : Necesito más....
- It's more complicated than you think : Es más complicado de lo que tú crees.
Más is used to form the comparative and superlative forms in spanish.
- He is taller than Peter - Él es más alto que Peter.
-Paris is the most amazing place I've been - .París es el lugar más asombroso en el que he estado.
You should not cofuse "MÁS" with "MAS" (without the accent, that is a conjunction) that means "BUT"
(instead of "mas" you can use "pero" or "sin embargo"... all have the same meaning, but "mas" is more poetic and used more in literature, or when you want to sound more highbrow LOL!)
-I waited for her, but she didn't come: Estuve esperándola, pero ella no vino / Estuve esperándola, sin embargo, ella no vino./ Estuve esperándola, mas ella no vino.