Need help understanding Mifare

Hi all
 
First and foremost I just want to say I have googled this subject extensively before posting this question. and I am asking only those who has experience in working with this technology. Because i have absolute zero experience in it.
 
I have the following questions: Regarding desfire EV1 (8kb)
What is the significance of the key a and key b ?
What is the desfire initialization procedure ?
What data structure is to be expected when i read from the card ?
How to encode a custom value into the cards sectors and how it works ?
What to look for when programming the reader to read the cards sectors ?
 
I am looking for a mechanic like explanation for example:
To Encode a card make sure that . . . , then do this, run this command ect.
 
I am not really looking for code just a more high level explanation short of breaking apart the bytes and the bits (there are more than enough of that on google).
 
but if you can point me in the direction of a article of STEPS a programmer should take when working with this please let me know.
 
Thanx in advance