As per wikipedia the Black Scholes assumption is:
random walk) The instantaneous log returns of the stock price is an infinitesimal random walk with drift; more precisely, it is a geometric Brownian motion
But later on, under section, under this section to the right, there is picture and it says:
The normality assumption of the Black–Scholes model does not capture extreme movements such as stock market crashes.
So does it assume a normal distribution or a GBM with drift?