What is RAM?
In one sentence: A computer's working memory: very fast, holds what programs are using right now, and goes blank when the power goes off.
A little more
RAM (random-access memory) is where a computer, phone, tablet or games console keeps everything it is working on right now: the open apps, the web page you're reading, where your character is standing in a game. It is extremely fast, so programs can change things in it millions of times a second.
RAM keeps information as tiny electric charges that leak away almost instantly, so it must be refreshed constantly and is wiped when the power goes off. That's why games and documents have to be saved to storage (flash or a disk), which keeps data with no power at all.
It's a bit like… A desk where you spread out your homework: quick to use, but it's cleared every night. Storage is the drawer you put things in to keep.