system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: How does RAM work?
gpt
Imagine you have to do research in a library.  So you (the CPU) go to the library (the computer) and walk though the ailes (the hard drive) collecting books (data) on the topic (the computing task).  You take your books and sit down at a desk and stack all your books in a pile on the corner (RAM).  As you read through the books you end up keeping some of them open in front of you as you reference them frequently  (cache).  As you read them and process the data, you are writing your report (the processes result).  

Note the relationship between your types of storage space and how fast you can reference them.  You can only have a couple books open at a time in front of you as you are skipping around reading them, but it is really fast to do so.  You can always reach over, grab a different book from the stack on the table, and replace one of the currently open books.  It takes a little bit of time to flip through the pages and find what it is you are looking for but the process is still relatively fast.  If you realize you don't have a required book on the table (the data isn't loaded into RAM) you then have to get up and wander around the library to find the book (like when your computer is taking its time turning on or opening a program for the first time).  There is one slower method of data retrieval-  when the library doesn't have the book and you have to request it from another library (pulling data over a network, aka the Internet).

A multi-core processor is when there are multiple people at the same desk doing research.  The desk space fills up pretty fast you you definitely want a big desk (lots of RAM) or it will slow everyone down because they don't have much space to store their books.

Dynamic RAM, like what you hear when you say your computer as 4 or 8 or 16GB of ram, is temporary - meaning that every night the librarian comes through and clears off your desk.  You have to start fresh every time you leave. These are the sticks of RAM that are sticking out of motherboards that you can upgrade if needed.

Static RAM, like the Flash memory of your phone or a solid state drive, is kinda like being allowed to keep your books on the a special table overnight an no one touches them.

Lots of RAM is expensive in a system (you can only put so may tables in a library) but it definatly speeds things up.  If you have "too much" RAM it doesn't really help you (how may books will you ever realistically need on any topic to find the answer?) in most cases unless you are doing some pretty high end stuff (NOT surfing the Internet or writing an email).

Cache is RAM that is built into the CPU, where space is at an extreme premium.   It's fast as hell, but very expensive.