They're missions with different conditions, such as ""Reach Player Rank 50,"" which grant Titles upon completion.
You can set up one Main Title, and two Sub-Titles under ""Titles & Profile."" These will be visible to other players in the Co-op Show matching screen.
Some Titles grant bonuses to Talent. To find out more, go to Menu > Titles & Profile, then tap and hold a Title to display Title Settings. Tap and hold Titles you already own, or tap Titles you haven't yet unlocked to read more about them.
You don't need to assign Titles for their Talent Bonus to take effect. Just owning them is enough.