The Decisions section explains Initiative basics.
Working with Customers in an Initiative
At the last step of the Initiative creation wizard you will have this choice
The ‘Don’t allow collaborators to see each other’ setting means that the collaborators you invite will see it as if you only invited them. They will not see or be aware of each other or each other’s votes or comments.
This setting, which can only be changed during creation, is a good option if you are getting votes from participants where you would rather they not be biased by each other’s opinions.