The alanning:roles Meteor package provides Reaction permissions support.
Permission Groups are are way to grant multiple users a group of permissions. The Accounts Dashboard provides a way to create a group and add users to them. Reaction currently ships with the four groups: Guest, Customer, Shop Manager and Owner. The Shop Manager and Owner groups are admin groups. Guest group is by default for anonymous (un-registered) users while Customer group is by default for registered users (users who created accounts).