Some background context (assuming you're already roughly familiar with OpenStreetMap):

• StreetComplete is an Android-exclusive app that acts as an extremely trimmed-down, gamified way to contribute to OpenStreetMap. You don't contribute new structures, but rather you fill in details about existing ones.
• It'll ask you questions about existing structures like "How many levels does this building have?" or "What is the surface of this bike path?" These are called "quests", and it's expected (see: Bro Code, Division 6, Chapter 5, §32) that you're either there in person surveying or have been there recently and absolutely know that you're correct. The visual presentation is extremely smooth and beginner-friendly.
• This is helpful not just to new users but to people who don't ever want to get deep into editing the map. (It can also help regular contributors notice small details they accidentally missed in an area.) A bunch of non-power-users contributing small details goes a long way to making the map actually robust and arguably better than services like GMaps – instead of just something that a few privacy/FOSS advocates vocally use and giant corporations silently use.
• Go Map!! is a robust editor for iOS, kind of like an analog of Vespucci on Android.

However, I learned that Go Map!! isn't just a robust editor; you can also use it to contribute to StreetComplete's index of quests.

Why YSK: if you or a friend has an iOS device, this is a great way to contribute to OpenStreetMap with a very streamlined UI that acts more like a game than it does mapping software. I didn't know this before and would often only bring up StreetComplete and hope the other person has Android.