Let's say I am going from the Low E string to high E string. I will start with a downstroke then upstroke then downstroke, now since I wanna go to the next string which is right below and that I already have my pick going down from the downstroke I will continu the mouvement into a downstroke on the next string.
so it's D - U - D (let the pick motion go down on the next string) D - U - D .... and so on.
Same thing if I go from high E to Low E string but then I would start with an Upstroke. So U - D - U (keep the motion of the pick going upward) U - D - U.
There's probably a very cool technical term for that but I don't know it honestly. lol