From MHWiki

HornTracker is a community-run database that collects information about each hunt (what cheese, weapon, base, and charm were in use, what mouse was attracted, and so on), as well as other game statistics (what a Special item contained when opened, how many Crowns a hunter has obtained, and so on). Data is collected by installing an add-on to the Firefox or Chrome browser. This data can then be used to make predictions about best setups, likelihood of getting a particular item of Loot, or any other use where tracking past trends may provide more insights into the game.