The Alpha Transparency in Game Maker is the visibility or "fadedness" of text or sprites. The level of Alpha Transparency can be changed using the draw_set_alpha (for text) or image_alpha(for sprites) functions.
This would make the text draw very transparent.
This function can be used in a step event to create a fading text or sprite.
An Example (In Step Event requiring variable "textfade to be set to 1 in create event":
textfade=textfade - .01 draw_set_alpha(textfade);