The Black Scholes Model is a model for options pricing.
The model assumes that movements in the underlying follow a geometric Brownian motion with constant drift and volatility. The constant volatility of the Black-Scholes model corresponds to the assumption that the underlying asset follows a lognormal stochastic process.
Scholes won the Nobel Prize in 1997, but in 1998 his Long Term Capital Management blew up in the Russian financial crisis.