StreetComplete is a really fun and accessible way to contribute to OpenStreetMap from an Android device - walk around in your local neighbourhood (or anywhere really) and solve 'quests' by answering questions about the things around you!
You don't need to learn anything about mapping conventions, or infrastructure, or about the more complex mapping tools that exist for OpenStreetMap. The app will explain everything to you that you need to know, when you need to know it, and ask easily understandable questions with reference pictures for the answers.
The only setup needed is to make an OSM account and log into it from the app, so that it can upload your answers - and you can also do that at any later time, after trying out the app without an account for a while first. You can just install it and go outside right away!
The app doesn't need any cellular internet connection; it can work offline and synchronize your answers once you reach a place with eg. WiFi. It's also quite performant, and should run well even on lower-end phones. There is also a 'multiplayer' option that lets you split up in teams and each tackle different quests in the area.
