GPS
To go geocaching, you need a GPS
To go Geocaching, I use a Garmin Quest II GPS. I've bought it here. There's a very informative forum about all kinds of GPS's here.
Next to this "antique" GPS, I use the Garmin Zumo 660. It's batteries aren't equipped to take long hikes, so I still use the Quest II.
More modern, I also use the GPS built into my Samsung Galaxy S7 mobile phone in combination with the c:geo-app
Geocaching
If you have a GPS, you can go and try to find a stash, cache, treasure. For free!
To select a cache, I frequently have a look
here. The underlaying database is here. My team and I
use the teamname "Mike enzo".
