Ok so this is kinda complicated but I'll explain anyway. So Destiny is not the traditional MMO like WOW is. It is a totally new genre known as a Shared World Shooter. Pretty much you will be playing in a smaller "private" area where there is just you and your squad mates which is usually 2-3 people. In these areas whereas in a MMO where you would she everyone in that area in destiny you will only see your squad mates even if others are in the area. That being said all of a sudden you might be just running around and a public event where a enemy ship will just come in and drop off tropes and a giant tank or boss or something. At this point random people from around that you wouldn't be able to see will just appear and run out from somewhere. This will probable be groups of 7-20 people (20 people being the maximum they would ever consider). So the next thing that could happen is just that regular campaign missions at points would offer boss fights that are also so big that you will need help. There will also be dungeon like places that will require 2-4 squads most likely and will just be a fun place to try and conquer. Ok also there are gonna be raids that require at minimum 6 people squads at the very least. These will be huge battles where you will fight pretty much a huge city/stronghold. One thing to mention is it is a dynamic world meaning what other players do might also effect your game and also there is a behind the scenes menu so there is no waiting to join a game. Although that stuff does happen it happens behind closed doors so you won't physically see these menus like, joining a match looking for a match etc. Its complicated but awesome. But also there will be a feature to join friends and stuff but instead of the traditional loading menus you will probably just see your spaceship flying through space or something like that. There will be menus but they will mostly be used to get to places store loot do faction battles etc. Hope this helped even though it's really long (thats what she said)