How do some websites make money?

There are different ways in which various website (Facebook, Twitter, Google) monetize their services:

• Investors pour money into any company because they believe that it touches 200 million people every day. They want to reach (control) this market place.
• The company builds a platform and offers a really open API. They then allow several other people to develop applications on their platform, for free. The platform provider then uses their analytic monitors to determine which apps are doing best and decide to buy the apps which look most promising. These companies chose not to make money directly, as a platform owner. Instead they keep watchful eyes on which applications are going to make money; and they buy those apps.
• They generate revenue from advertising: it is estimated that in 2017, each Facebook user will generate $17.50 in advertising revenue every year while a Twitter user will make $12.56 for the company per year.
• Twitter invented “Promoted Tweets” which will show up when Twitter users search for keywords that the advertisers have bought to link to their ads.
• Yahoo offers "sponsored trending topics" where an advertiser pays to appear on the current list of trending topic by users.
• When people search Google using a keyword, the resulting list and relevant ads are shown according to prescribed ranking determined by the highest bidder.
• Sending SMSs is not a negligible source of revenue. Businesses like Skype can make a lot of money by charging tens of millions of users a small fee for sending/broadcasting info/tweets/ads. It’s a very good profit model with very low operating expenses, and minimum spending on labor or materials.

CPM (cost per mille) is the amount an advertiser pays to have his ads served against videos 1,000 times. Each time an ad on a video runs completely & not on a mobile, it’s called an impression. By contrast, if a website owner wishes to monetize his blog by offering advertising space, Google or YouTube apply the CPM rule when paying you. A website owner receives a share of their cost per million clicks on ads after they take their cut and pay you after accumulating $100 per month.