Nylon and steel strings are two totally different guitars.
Nylon has wider frets and is mostly used for classical music or flamenco etc..
It's held differently in your lap and you use your right hand fingernails mostly to play. (using it the standard way most people use classical guitars that is)

Steel string is closer to an electric except the strings are heavier and there's no amplification. Plus you can use it for numerous types of music whereas a nylon string is more suited to a particular style.