But, the only thing Alpha does is telling Glide how to transform the RGB values. We'll give an example called Alpha Blending. Alpha Blending is a technique to make triangles transparent, so you can see the underlying triangle through the upper one. This is often used as a window, you can see the window, but you can also see what's behind the window. The grade of transparency is set by Alpha.
Alpha has many uses.
I've already explained what Alpha Blending is. Aliasing occurs when you draw a line that is nearly vertical or horizontal. They appear to be jagged. Anti-aliasing is a technique which reduces this by coloring neighboring pixels. This process though, is very slow and I advice you only to use it, if you can live with the poor performance.