How facebook generates its revenues?

Factual Questions
1

I want to know how facebook used to generate its revenue before IPO and how it’s generating the same after IPO?

Are there any changes in their revenue generation strategies after IPO??

Well, I already know that their main source of income is advertisement, but i would love to have some insights.

2

Here is an article I found by googling “how facebook makes money”.

Here is another.

How that changed after IPO or whatever, I can not help you with.

3

As an aside, how does all this work for people with Adblock? I never see any advertising and wonder why anyone would put up with it when the solution is really simple to implement.