The North Korean government heavily restricts what you can do there. Here is a short list of the main restrictions I remember facing.
You may not take pictures without permission. On the other hand, if you treat your guides well and tip people, you get a lot more leeway.
You may only visit sites from the list of places the government allows you to see. You can only get there by the bus they take you in. I understand Koryo, the Beijing-based company that brought us, pushes to expand that list and gets new places on the list sometimes. I bet if you worked with them you could get to be one of only a few non-North Koreans to visit some places.
You may only go places escorted by your guides. You must listen to the official history and description of each place. Some sites had extensive mandatory parts, especially the mausoleum containing the embalmed body of Kim Il Sung. I hope I get to describe that place, though I won’t be able to do it justice. It was another world, even in a country that was another world.
You may only eat in approved restaurants. You may only stay in approved hotels. The guides ate separately from us.
You may not talk to any North Koreans besides the guides and staff at the approved sites, restaurants, and hotels. We had a few occasions to get around this rule, specifically playing ultimate, at the Mass Dance, and at the amusement park. The amusement park featured a North Korean guy hitting on Ingrid, which probably happens rarely, but counts as communication in my book.
At one point I walked from our group to throw away a piece of trash in a trash can by a bus stop. On my way back one of our guides got very incensed at me, asking what I did and why and looking very cross at me. When I looked back at where he was pointing, a young kid was sitting at the bus stop. I hadn’t even seen her. I think he was worried I had spoken or interacted with her.
You may not spend North Korean currency. You can buy it as a souvenir but you may not spend it. That makes sense because the North Korean government needs foreign currency to buy things overseas. I doubt anyone outside of North Korea would accept North Korean currency for anything.