I'm reading about expectation maximization from Dempster, Laird and Rubin's original paper which can be found from the following link:
My questions are from pages 1 and 2. I have added those particular parts into the image below and tried to be as clear as possible with my questions (4 questions in the image, highlighted with red numbers 1, 2, 3, 4). Hope someone could make things clearer for me :)
To summarize my questions in the picture are:
1) Have I understood the relationship between the variables correctly?
2) What does the text in the green box mean exactly?
3) How to interpret these formulas
4) WHAT IS GOING ON HERE?!...this doesn't seem clear at all! x)