Your pattern should tell you somewhere what they mean by that. If so and you don't understand it you could put the directions for the stitch here and we'll try again.
I did a search and find that sometimes knitting alternate stitches with 2 different colors is called salt and pepper. For instance if you had black and white and did it like this:
These don't line up properly because a "W" and a "B" are not the same size but that is the idea alternate and then on the next row alternate in the reverse order.
I did find a stitch called Salt and Pepper Tweed, but it did not give the directions.