Some newbie question

[maggocnx]

Hello everybody. I use Linux for a while allready, but this is my first project which is going so deep. I collected this questions during my first days with the Olimex A13 board. I followed the steps in https://www.olimex.com/wiki/Build_Bootable_SD_Card_with_Debian to build the debian sd card. I got Wifi running, can login via ssh, installed xserver and can run simple programms on a monitor. I will connect an LCD and other hardware later, but for know I have some questions for general understanding and software.

1. When I followed the instruction for building the image, what did I actually do? Everything is running but I not really understand what really happend. Did I compile the linux kernel ? How did I get it to the sd card (copy the contents from out/lib/modules/3.0.42 to sdcard ?). Are these modules the kernel ? What is u-boot for ? 

2. Where do i put my software projects.  I want do develop my own sofware and also drivers for some hardware components.
As long I don't need to include anything it works. If i want to make my own modules, where do i need to place my source files ? Do i need to put them somewhere in my linux-sunxi folder ? Where to find libraries like <linux/module.h> .

3. I managed it allready to cross compile and run a helloWorld programm. But its only working when I compile it with the option --static. What do i need to install on the A13 boards to run it with shared libraries.

4. In eclipse is set toolchain to arm-linux-gnueabi- in the example http://www.agilart.com/blog/debugging-on-embedded-using-opensource-tools-part-1  they use arm-unknown-linux-gnueabi- . Does this matter in any way?

Thanks in advance I hope i can give something back when i am more advanced with this topic.