Rising through the ranks

Challenges are ways to track your progress through the game's content.
Not only you track how your progress through game content is going, but you also can be rewarded with Titles for your work.
Whenever you need something to look forward to, some content or ideas, you can check your challenges and go get your titles.
Not only that, some may be very simple and straightforward, but some are either extremely hard or time consuming to be done.
Depending on the difficulty of the challenge that is completed, a different score will be awarded, and getting enough points will raise your Hunter Rank.
Challenges are a way for you to find ways to push the limits of your character and to know what to expect from the game.
Types of Challenges

They come in six variations:
Personal: Challenges associated with your character directly. They measure how high your given stats can be and what they can do.
Exploration: Associated with regular game content. Clearing quests, tasks, visiting places or other world related things.
Conquest: Killing Bosses, high value targets, difficult quests, completion of multiple objectives and others.
Social: Interaction with community, party challenges, use of features, cathedral and nocturne activities.
Unique Items: Finding or looting specific rare items, doing specific quests for hidden rewards, treasures or special items.
Legendary Feat: Hardest challenges, requirements and specifically difficult content not for the average player.
Finishing specific regions, group of challenges and others will award you with a Title, that can be equipped through the equipment window's 3rd tab.
Titles are cosmetic only and a way to show off your feats. Some NPCs may also acknowledge some of those.
Hunter Rank

Completing challenges award you with higher hunter ranks.
These are not only for showing off or to obtain unique titles, but they are also tracked and different interactions may be available depending on your rank.
The Highest hunter Rank possible is Rank 9. Some special things may be available only to specific ranks.