Strike | Types of missions Destiny Guide

One of the objectives

Strikes are co-op missions for 3 players. Just like Story, Strikes have a recommended level and objectives set in advance. The players have to complete various tasks while fighting large groups of enemies and one or few bosses. Strikes don't start in a closed location. The team can explore the world and start the challenge when they want to. After you go to the mission's area, the team will be transported to a closed space and start a Strike.

Aside from regular Strikes, their three special types are also available: Vanguard Strike, Heroic Strike and Nightfall Strike. The first one is connected to Vanguard faction and lets you go on random Strike missions with a higher difficulty. The players will get Vanguard points and reputation that let them get equipment from this faction. Heroic and Nightfall are weekly Strikes that don't support random teams. They have a much higher level of difficulty and modifiers that introduce additional game mechanics. Heroic requires level 22, Nightfall - 28.