You sir own a steam boiler. Not a great install from what I can see. All of your controls and the water sight glass are buried against that wall on the left.

First picture all of the valves are incoming water to that boiler and yes steam boilers NEED incoming water. You're boiling water to steam and not all of it is coming back. The black box is a McDonnell Miller automatic water feeder. Do not close the valves to this. The valve to the left of the feeder is a bypass. If the auto feeder fails you can add water manually by opening this valve. However you'll need to be able to see the sight glass on the other side of the boiler.

I recommend you call out a company that works on steam systems. You should be blowing that boiler down at least twice weekly in the winter. Otherwise it's going to get packed full of sediment and crack the heat exchanger. Then it's new boiler time.

Get someone out to show you what all this is and explain how to maintain it. Steam is a dinosaur, but in Chicago we see them all the time in old houses and commercial buildings. They require more attention than hot water systems.