What is the difference between LPDDR3 and DDR4 RAM?
DDR4 is usually a bit faster, but LPDDR3 has less power draw and therefore is used in notebooks.
Virtual memory (RAM) is the space where programs and data are kept when they’re not currently being used. It’s a “virtual” location because it isn’t really physical; there’s no giant unused warehouse full of computer chips that can be accessed at any time, though you’ll see this type of PR from Intel sometimes.
If you have an app running on your phone that sucks up 2GB of memory–it’ll show up in RAM as consuming 2GB system-wide even though only 1 gigabyte of that will actually be necessary to run the app itself–then as soon as you switch to any other app, that 2GB is “freed” and can be used to run a different program.