Flacko has written
The RAM memory is where the variables, images, audio and other kinds of resources are saved to access them.
More RAM won't make your computer faster, but it will be able to store more data from running applications.
The reason that sellers only put RAM, screen size, and shit in their offers is because people tend to think "Moar ram is moar speed!" but that's wrong, sellers want people to think that because RAM memory is cheap compared to other PC components.