Flashpoint
From Destinypedia, the Destiny wiki
A Flashpoint is a weekly challenge given by Cayde-6 in Destiny 2.
One Destination is chosen for Guardians to focus their efforts on by completing Public Events. Participating in a Public Event but not completing the objective before the timer runs out grants 7% towards the Flashpoint; completing a normal Public Event grants 15%; completing a Heroic Public Event grants 25%. Completing the Flashpoint rewards a Luminous Engram, which can drop Nightfall-quality loot.
The PvP equivalent of this activity is the weekly Call to Arms.