How are super-fast websites accomplished? [on hold]

As an anspiring web designer/developer trying to build up my portfolio, a trend I've increasingly noticed lately is (multi-page) websites loading their pages dynamically rather than statically, with the result being that pages tend to load in a second or less. I understand that, as it's dynamic (or I'm assuming it is), it must have something to do with a scripting language, but in specific terms, what are the different ways that this kind of effect is built - what technologies and languages are usually used? I'm looking for an overview of the ways in which the effect is accomplished by most sites, so I can pick one and take it in the direction of more in-depth research so I can learn to use it on the sites I develop.

Thanks in advance!