Accelerated Mobile Pages is a relatively new initative supported by amongst others Google. In short it's a new "standard" of sorts for making really fast mobile web pages. If you want to read the official details on it, you will find that here.
Just to be clear, this is a very needed initiative, but the fact that it is needed is a huge failure. This entire "standard" is basically the ultimate proof that the vast majority of web developers out there are just not capable, or given enough time, to produce reasonably performant web pages, and that downright sucks.
People are slowly realizing that poor performance is hurting engagement, people have very short attention spans and just don't want to sit around and wait for a page to load. Making your page faster will make your visitors happier, its as easy as that.
Now the really sad fact is that AMP is actually slightly bloated for a number of uses. For one it requires the loading of a external script file, which really, most content based websites could probably do without. (It is loaded async though, so it is not render blocking at least).