Questions about drawing bitmaps

I’m trying to go through the wiki and the example sketches but I’m a little new to programming and have some questions about drawing bitmaps, their placement etc.

What I don’t understand is from this chunk of code from the Bitmaps example:

// to use drawBitmap, must cast the pointer to pixelmatixlogo as (const gimp32x32bitmap*)
drawBitmap(x,y,(const gimp32x32bitmap*)&pixelmatixlogo);

I was able to get my 3 logos in the spots I wanted by tweaking the example to this:

// to use drawBitmap, must cast the pointer to gimp32x32bitmap as (const gimp32x32bitmap*)
drawBitmap(0,0,(const gimp32x32bitmap*)&oneBitmap);
drawBitmap(0,23,(const gimp32x32bitmap*)&twoBitmap);
drawBitmap(0,46,(const gimp32x32bitmap*)&threeBitmap);

Why is gimp32x32bitmap being referenced in the sketch? What does the commented text mean? These will be 3 static bitmaps that won’t require redrawing and I plan on adding some updating text that changes colours, is backgroundLayer.fillScreen needed?

Without that, it’s hard to interpret the C source bitmap code exported from GIMP. It’s there so you don’t have to manually modify each exported bitmap. Check out the other files included in the Bitmaps sketch for more details