I did a guide somewhat recently on getting kids started in game development, where I went in to a fair bit of detail about the various options, including GameMaker.

I can understand how the OP might be a bit confused over what it is, even with Googling, as it's a bit of a hybrid, and can be a bit confusing especially if new. Plus, I kinda found Yoyo's site does a kinda crap job. It's a cross between an application, a programming language, a visual scripting system, an IDE and a bundling of tools needed to make a game. Basically it's a game creation kit in a box, just in the digital age, there are no boxes anymore.

Oh, and even though my guide was aimed at kids, it doesn't mean these tools are only appropriate for kids. Some very successful commercial games ( Spelunky and Hotline Miami come to mind ) were created using Gamemaker.

That all said, it's possible the OP was also just being lazy...

whether it is better for production quality games or just prototypes, is debatable

Yes, that's exactly what I have been thinking about for the past 3 months while working with construct 2. It seems that these tools can help you progress really fast but not too far, so for small games they are good enough, but as your project gets larger these tools show some limitations.

I find it difficult to transition from programming to using these tools, there's always a voice inside your head that tells you you're not doing it right. However it seems that most of Game Maker like programs are made for non-programmers who still want to make games. I think it's not fair to not be able to make games if you lack programming skills, lots of great game designers don't know how to code to some extent. These tools provide an opportunity to test your ideas and play them in few minutes or hours of work, I think it's amazing.

One more signifant complaint is the pricing, for a 2D software.

Construct 2 and Stencyl are cheaper, and for my specific needs, they proved to be more useful than Game Maker.