I could go into great detail and compile a large amount of information copy pasted from various sources; however instead I will refer you to good quality existing information to save both me and you time.
If IT Fits Your Macros - The Flexible Diet
"IFYM is a flexible dieting approach where you disregard arbitrary food labels such as “junk food” and “clean food” and focus on your total caloric intake (calories in versus calories out), your daily set macro-nutrient targets (your fats, carbs, protein), and your micro-nutrient goals (your vitamins and minerals) in order to achieve your desired body composition." - DoYouEven.com
The basics of IIFYM :
http://doyoueven.com/2013/01/iifympart1/
http://iifym.com/introduction-to-iifym/
Videos explaining IIFYM :
http://www.youtube.com/watch?v=BC7qX3qr5Yc
http://www.youtube.com/watch?v=oWD564rZDYA
Calculating your Macros:
http://iifym.com/iifym-calculator/
(Various formulas, the first two listed are not as accurate as the other two)
http://doyoueven.com/2013/01/iifympart2/
(Good explanation on calculations.)
Popular fitness youtubers thoughts on IIFYM:
Alberto Nunez:
http://www.youtube.com/watch?v=f99jPRSgVjg
Chris Jones:
http://www.youtube.com/watch?v=HMS7KRe-InI
Omar:
http://www.youtube.com/watch?v=XZC_Em6GtjY
Elliot of Strengthcamp:
http://www.youtube.com/watch?v=3wNwvOrwv_k
Clean eating vs IIFYM - Controversial Topic:
http://www.3dmusclejourney.com/articles-clean-eating-vs-iifym.php
http://www.shreddednation.com/clean-eating-vs-iifym-layne-norton/
http://www.shreddedknowledge.com/home/a-talk-with-the-doc-dr-layne-norton/
Clean eating or IIFYM? You decide. It comes down to personal preference, experience and your beliefs.