Street Complete has a map with an overlay that looks kind of like the Pokemon Go map, but it has lots of different icons where it needs more data. Tapping an icon will give you a question based on the icon type, and will be something like ‘what is the road surface here’, or what is the number of this building '.
It’s pretty easy to use, and if you don’t know the answer, or are not confident about answering it, you don’t have to.
Like you say, with OpenStreetMap itself, you don’t get questions and you add things directly to the map manually. It can sound complicated, but you can do anything from adding a single node (a dot) and marking it as the tree in the town square, to drawing a box and labeling it as a building, all the way up to adding bus routes and power lines, like one person on the Discord is doing around Wales at the moment.
As long as the thing actually exists on the ground, you can add it to OSM, and you can do as much or as little as you like. Any detail is better than no detail 👍