Anotomy of "applet" directory

Just curious about Ardiuno internals here. On export, a directory called “applet” is created next to the .pde file. What’s going on in there? Now I appreciate Ardiuno was designed to make these kind of questions reduntant, but it’s always nice to know, then forget about it!

Some things I do know. There is a .c file, which is I guess a C version of the original .pde. It strips out the .pde comments, and calls a header file from Ardiuno Install/lib/targets/arduino/WProgram.h which in turn includes other C files specific to the Atmel microprocessor. open WProgram.h in a text editor to see what these other files are.

Then there is a .hex file, this is the file that gets put on the Atmel during “Upload to board”. It is, I think, an assembled version of the compiled .c file (along with the included .h and .c files described above), and I think the compiled c file is .c.o

OK, running out of ideas here, and probably over complicating things. Anyone else able to shed some light?