destiny 2 is a multiplayer first-person shooter video game which is the sequel to 2014's Destiny and it's subsequent expansions. Unlike the original Destiny where you communicated with other players using the consoles messaging system in Destiny 2 players use a new feature called 'Guided Games' which allows you to search for clans who may need additional players for activities such as strikes or raids. Activities in Destiny 2 are the same as the original, they are divided among player versus environment (PvE) and player versus player (PvP) game types.
The sequel takes place one year after the events of the Destiny: Rise of Iron DLC. The Last City and final bastion of humanity has fallen to Ghaul, the commander of the Red Legion who has stripped the city's Guardians of their power and forced the survivors to flee the Tower. Now powerless the Guardians must venture to mysterious new world worlds to acquire new powers to confront Ghaul and the Red Legion and reclaim humanity's home.
The video below goes over the full timeline of Destiny including the major events, key characters, lore, backstories and other elements of Destiny's universe that you'll need to know to be up to date.