Xander 99-40, the Bounty Tracker, is where you accept & complete Daily Bounties. Each day, there are five new Vanguard (PVE) and Crucible (PVP) bounties added. Since Guardian bounty slots have been expanded from 5 to 10, you are able to carry a
On rare occasions, you will randomly be given a Vanguard Mentor Missive after completing a bounty. This missive, when turned in to the Bounty Tracker, will offer you an option of three Exotic Bounties (choosing one). Note: You do not need to choose immediately; you can allow the missive to remain in a bounty slot until you've chosen.
While bounties for Special Events (Queen's Wrath, Iron Banner) had previously been handled by the Bounty Tracker, they are typically now handled by their specific vendor.
Grimoire > Tower Allies > Bounty Tracker
"There are many threats beyond the City's walls. To help track and eliminate these dangers, the Vanguard has initiated a bounty system to reward Guardians who take the fight to the City's enemies. Lord Shaxx, not to be outdone, lays out his own bounties for performance in the Crucible.
Xander 99-40, a recent product of the City's foundries, tracks every Guardian's progress and dispenses rewards."