It might be easier to understand what Grids does if you think about a grid of buttons like OXI One's. Imagine that each button on the grid corresponds to a different pre-programmed pattern. You select a button, and the column that the button is in on the grid (counting from the left column towards the right) is the X value. The row that the button is in on the grid (counting from the top down) is the Y value. So X and Y are just a way of telling the pattern generator which button you want on the grid, and hence which pre-programmed pattern will play. The reason it's laid out in this two dimensional way instead of just a list of patterns is that you can blend between patterns by selecting X and Y values that are actually "in between" the grid buttons. This concept and the patterns themselves come from the Eurorack module Grids, by Mutable Instruments (hence it's MI Grids rather than M1 Grids).
