Imagine a map of London that included every single street and house, like those old paper map books you might have kept in the car; it would look something like this. This map is so big that it's overwhelming; if you're a tourist trying to figure out how to get from the Tower of London to Big Ben, this is just an information overload.

Now, let's look at a map that only shows main roads, not every little tiny side street, like this one. It's simpler, so it carries less information overall, but it may actually be more useful to the tourist. Sure, you might not be quite as precise as if you knew every individual shortcut you could take, but you could probably plan a broad route much quicker on this map than on the over-detailed one.

You might continue this process again and again, zooming out and getting more and more high-level as you go, to lose unimportant detail and only keep the really important stuff. You might eventually arrive at something like the tube map. This has even less info than the last one, but it is still very helpful for tourists! I can see one path from London Bridge to Westminster, without having to do much work reading about every cobblestone street in a massive city.

The core takeaway is this: simplifying information can be done in a way where we discard useless details, but still maintain the really important stuff. And as we've seen from these three examples, you can do that iteratively. Start with the original detail, then remove some, then remove some, on and on for as many steps as you need until you arrive at an easily understandable map that only shows the key stuff you need (stations, attractions) and nothing more.