As an improvisor the number one question I get asked is, "Do you guys really just make up all of that stuff on the spot?" and my answer is always, "Yes, that's why it's called improv." Everything that you see is made up in front of you for better or worse. I don't get upset when people ask me this because it usually means that it was a good show. Something so funny or artistic that they can't believe that we made it up right then and there. No one questions improv when it goes bad. I've never heard, "Was that abortion scene in the old folks home really just made up?".
Some audience members treat improv like a magic show. They think that the performers are trying to mislead them and they don't want to look stupid. Instead of just enjoying the show they are making up conspiracy theories in their head. Yes, I understand that maybe sometime, somewhere some horrible improvisors tried to block out a scene before the show, but I guarantee you that that scene wasn't as good as the fully improvised scenes that were discovered on stage and will be remembered by audience members for years.
So how is it possible? How can a group of people build a show when they have no idea what's going to happen? The quickest answer is, "yes and". This means agreeing with what someone else had said and building off of that. It's the number one rule of improv and it's basically the only rule in improv that you can't break. It takes awhile to learn and understand this rule because it goes against everything you've learned as a normal person. Most of us are programed to think things through and try and find the best solution to a problem. Unfortunately as improvisors on stage we don't have the luxury of doing this and instead have to support each others random ideas. Otherwise if we just say "NO" to each other the scene is stuck in neutral and the audience is regretting their decision to pay $5 to see this garbage.
Saying yes to things on stage allows the scene to move forward and organic characters develop. As an improv actor there is no better feeling in the world then discovering everything about my character within the first few lines of dialog, knowing that this is going to be a good scene, and that I could almost go on forever with it.
So yes, improv is real. I love improv because of how real it is. It's more real than any TV show or sketch can ever be. You're allowed to change anything and discover anything. It's something that not only develops right in front of the audience, but in the improvisors on stage. Performers and audience members discover things together and share an experience that will never happen again. It's a true art form and there is no better place to learn it, perform it, or see it, than Chicago.