This is a summary of Multiplayer in Saints Row IV
A player cannot join a session where the host is in a mission or activity. Doing this either has the guest wait or require the host restart the mission or activity.
One player cheating affects the other. If a guest has cheats, the host has the option to kick them before they join.
Co-op is where 2 players take part in story missions and other activities. The co-op partner is displayed as a homie and takes up a space, and their health can be seen above their characters. If the partner is downed, the player has a certain time to revive them, much like homies. The player also gets paused if the partner pauses.
There are 2 different types of competitive activities that players can participate in.