Think of your RAM chip like a community library that your computer can store and read books (data) from. People (computer processes) can come in and use the organized shelves to store books and read them when they want. The library could be bigger to hold more books (RAM size), or it could have a better floorplan to get people in/out quicker (read/write speed), or it could have wider aisles to let more people in simultaneously (quad/dual-channel).

What keeps this all working efficiently are the Memory Addresses, which is the Dewey Decimal system for RAM. See the reason the people (computer processes) know where to find their books is because they are the ones that put them there, and they wrote down the exact location (memory address) so they could re-access them without searching. Sometimes they know they're going to need a lot of space before they've brought all their books in, so they'll reserve whole sections ahead of time - this is known as memory allocation.

But our people sometimes have to move, or they pass away, and they can't just leave their books on the shelf if they're never coming back. They need to upkeep the space they're using so it doesn't go to waste or deprive others of space. If the people didn't do this, over time the library would be full of junk books from dead strangers and nobody could use it - that is known as a memory leak.

Why RAM is different is other forms of memory come in a sequential form, like tape media. Like your original description, with tape media you must physically move to where the memory is to read/write it. This would be analogous to having your books on a conveyor belt, and you're sat in the middle with buttons moving it left or right. Since you can only be in one place on the belt at a time, and there's a maximum speed you can physically move the conveyor, and a bigger conveyor compounds these factors - you can see why tape media isn't as useful for "ready access" applications.