The world of Badge(r)s is a peaceful, relaxed and casual one, build on top of that real world, we actually live in. This is what they call a GPS based game.
You explore that world, just by moving around in the real world, and use the app as a window into the Badge(r)s world.
Once you look through that window, you will see items/badges nearby and elsewhere on that world.
You mainly grow and thrive (aka level) in Badge(r)s by both collecting badges you find and sharing the ones you produce.
With all that collecting going on, it is not about having the most, but about having many different types.
To share a badge, just drop it where you are, to pick up a badge, just get close enough and touch it on screen.
By dropping and taking, you will interact with other players without necessarily meeting them.
The system generates special badges about once a week, you might want to collect these weeklies also.
Beside trading, you can also level by exploration, i.e. taking and dropping in different places aka quadrants.
The app/window shows you which quadrants you have already played and which not.
On top of trading and exploring, there is a bit of competition for being the most comprehensive explorer of regions.
Regions are connected quadrants, connected in the sense of OpenStreetMap.
Having explored most quadrants of a region gets you the special mapper badge for that region, complementing your ever growing collection.
And, if you need, actually there is even a bit more competition for ruling regions.
Ruling a region can gain you a special ruler badge.
However to rule a region you essentially share your stuff, your self produced badges, in that region, so a mere and kind “invasion” of collectors picking up your badges might shake and crumble your little imperium.