Imagine that you have a task to "Prepare contract and sign with new employee" as a part of a "New employee onboarding" process. Contract should be signed with every new employee by someone in your HR team.
The problem is: if you have 5 HR managers - who should you assign this task?
To make a proper assignment you have to consider a lot of factors:
Who is available right now and not overloaded with other tasks?
Who is out of office?
Who has less tasks on hands?
Who is on vacation?
Solving this every time when new employee is on-boarded is a cumbersome task for a process manager.
To solve this problem in Metatask you can add multiple assignees for any task in a process template. You can use both groups and single users (although it's more convenient to create a group and add single users to it). In the situation described above you can just assign 'Send welcome email" task to the whole HR group:
Assigning a task to multiple people will make all of them assignment candidates for this task. That means the task will become available to all these people and any of them can take it from an "Available Tasks" list and assign it to self.
You can think of this as of shared pool with tasks available to the whole HR department to work on.
You can see all your available tasks on a right side of Tasks screen: