The p-variation is a generalization of the total variation of a function by replacing the absolute value of the increment in its definition by the p-th power of this increment. Then a.a. sample paths of a BM have bounded p-variation for each p >2. The usefulness of p-variation property for the Riemann-Steiljes integral was shown by L.C. Young (1936). We plan to discuss how the p-variation could be used in stochastic calculus and stock price modelling.