Caches are supply points managed by the MIB to support their Agents. They are spread out all around you on the map. Tap on a nearby Cache to retrieve its supplies.
You must take into consideration various safety factors when looking for a Cache (i.e., time of day, awareness of your surroundings, and not trespassing). Caches should all be located in public locations in order to be accessible for all players. If you see a Cache placed in an inappropriate location, tap on the Cache. Then tap on the GPS icon and fill out the Report Issue with Location form. Or contact Player Support.