Bungie has announced a new co-op system for Destiny 2 called Guided Games. The new system is primarily meant to support players who typically play solo, or to clans that need that important 6th member for their raids.
The Guided Games matchmaking is a way for solo players to help find clans who are looking for a solo player. Guided Games is a way for solo players who might be wary of clans to "test out" a clan.
It's a non-commital way for solo players to find new friends and for clans to find players to help them finish a raid or group event.
The story is developing and will update accordingly.