Memory & addresses
When a program runs, all its numbers, letters, and lists have to live somewhere. That somewhere is memory — RAM. The trick to understanding it is this: RAM is just one enormous row of tiny numbered boxes. Each box holds one small value, and each box has a number that says where it sits in the row. That number is called its 'address'. Once you see memory as 'a wall of numbered boxes', a lot of confusing computer stuff suddenly makes sense.
A wall of numbered boxes
Picture the wall of mailboxes at a post office: hundreds of identical little doors, each with a number on it — box 0, box 1, box 2, and on and on. Behind each door you can stash one small thing. RAM works exactly like that. It's a huge row of tiny boxes, each able to hold one small value (a number like 72, or a single letter like 'H'). And each box has a position number — box 0, box 1, box 2… — that never changes. That position number is the box's ADDRESS. So an address isn't anything fancy: it's just 'which box', the way 'mailbox 247' is just which mailbox.
Where your variables actually live
When you write `score = 10` in a program, the computer grabs a free box, drops the value 10 inside it, and remembers 'the variable called score lives in box number such-and-such'. The NAME 'score' is for you; the ADDRESS (the box number) is how the computer actually finds it. Later, when you ask for `score`, the computer doesn't search the whole wall — it goes straight to that box's address and reads what's inside. That's why computers can find a value instantly no matter how much memory they have: they don't hunt for it, they jump right to its box by its number. Every variable, every letter of text, every item in a list is sitting in some box at some address.
Memory vs. storage: fast-and-forgetful vs. slow-and-forever
People mix up two different things: memory (RAM) and storage (the disk). They are not the same. RAM is the computer's fast scratch space — the desk it works on RIGHT NOW. It's super quick to read and write, but it's TEMPORARY: the moment the power goes off, every box is wiped blank. That's why an unsaved document vanishes if your laptop dies. The disk (a hard drive or SSD) is storage. It's much slower than RAM, but it's PERMANENT — it keeps your files even with the power off. That's the difference between your desk (RAM: fast, but cleared every night) and your filing cabinet (disk: slow to dig through, but your papers are still there tomorrow). When you 'save' a file, you're copying it from the forgetful desk to the permanent cabinet.
Questions you might have
▸Is memory the same as storage / my disk?
No — they're two different things people often confuse. Memory (RAM) is fast, temporary scratch space the computer uses while a program is running; it's wiped when the power goes off. Storage (your disk or SSD) is slower but permanent — it keeps your files even when the computer is off. RAM is the desk you work on now; the disk is the filing cabinet that keeps things for tomorrow.
▸What exactly is an 'address'?
It's just the position number of a box in memory — 'which box'. Memory is a long row of tiny boxes numbered 0, 1, 2, and so on, and a box's address is its number in that row. Just like 'mailbox 247' tells the mail carrier exactly which door to open, an address tells the computer exactly which box to look in. Nothing fancier than that.
▸What happens to RAM when I turn off the computer?
It all gets wiped. RAM only holds its values while it has power; cut the power and every box goes blank. That's why you lose an unsaved document if your laptop suddenly dies — it was only ever in RAM. 'Saving' copies it onto the disk, which keeps things even with no power. So: always save your work, because RAM forgets everything the instant it's off.
▸How can one tiny box hold a whole number or a whole word?
It usually can't — one box only holds one small value, like a single number from 0 to 255 or one letter. Bigger things just use several boxes in a row. The word 'Hi' takes two boxes (one for 'H', one for 'i'); a big number takes a few boxes side by side. The computer just remembers the address of the first box and how many boxes the thing spans.
Best read after: What is an operating system?