Hi,
Sorry, but it will take hours be break down that code and explain every line in detail.
If you want to understand it rather than just use the code you will have to practice some assembler to gain the experience.
If you want to modify his code then its often easier to write your own code from scratch then at least you fully understand it.
You could try running the code in MPlabsSIM debugger, here you can follow the code through line by line and watch the registers being updated - though not all functions will work 100%.
You can see in the SIM screenshot below that the instruction "adc_samples : 3 * 18 " generates a block of memory, 54 bytes used, before allocating the next variable.