"Bar can sell you books on all of them, just so you know, but - so, some contagious diseases are caused by creatures so small you can't even see them, like how it's hard to see mites but much smaller, just kind of eating you from the inside, and they can be gotten off of surfaces by washing with soap and they can usually be killed by extreme heat, so for example by boiling water before you drink it. Vaccines can teach your body to recognize them in advance, which - so, you know how some creatures only get some diseases once in their lives? Vaccines let you skip straight to the part where you don't get them again. Complete with the thing where if there's anything really wrong with your immune system you'll still get them. They're like a nonmagical and slightly worse version of a disease ward. Computers are objects that can remember information and do math and do small nonmagical illusions of images and sounds, which in practice means you can do things like write a letter and have it sent almost as fast as if you were using paired artifacts, or ask it to multiply a bunch of numbers, or even have a public discussion forum where it's possible to remove instances of people showing up just to annoy everyone by reciting the entire alphabet. And if you don't already know about those, it's likely you don't know much about nonmagical automation, either - that's a thing where people use steam or electricity to make their tools move on their own. I would definitely recommend getting some books - and reading them here and copying them out by hand because they won't be in your language if you take them home."