What is the difference between drift …

In physics a drift velocity is the average velocity attained by charged particles, such as electrons, in a material due to an electric field. Applying an electric field adds to this random motion a small net flow in one direction; this is the drift. The drift velocity is directly proportional to current. The drift velocity is the average velocity that a particle, such as an electron, attains in a material due to an electric field. In general, an electron will propagate randomly in a conductor at the Fermi velocity. The average velocity of the free charges is called the drift velocity and is in the direction opposite to the electric field for electrons. The carriers of the current each have charges q and move with a drift velocity of magnitude vd. Current density is the electric current per unit area of cross-section.