This one should be required reading for all WP noobs. It can be a life saver. Put your phone down - you won't need it for this exercise.
Go to your computer, and go to
http://my.windowsphone.com. Take a look around. If you're already logged in, or once you're logged in, if you hover over your name, on the menu you can see your purchase history, for one thing. Reinstall apps that you've had. Nice if you've had to replace your phone, or if (like many of us recently did) you've upgraded to a newer phone. Got kids with Windows Phones? Use the My Family link there to manage them. I don't, so I don't know what all you can do there, but I would hope you can manage purchasing apps and such.
But there's one thing I want you to be able to find quickly, without having to think about. You can find it in a couple of places. First, right when you get to my.windowsphone.com (and other pages as well), on the left, you'll see links for find, ring, lock, or erase your phone, and you'll also see Find my Phone under the menu if you hover over your name. From there, you can do some important things if you've lost your phone (or if it was stolen). You can find it on a map (did you enable to location service in the settings, and the find my phone setting in settings?), you can lock it, even if you don't use a pin code on the lock screen, you can put a message on the lock screen, you can ring it even if it is set to silent, and you can wipe it clean, back to factory reset, should you fear you'll never see it again.
This is all baked into the phone. No apps to install, nothing to buy, no services to subscribe to. It just works. Like I said... This should be required reading.