In Adobe Target users have different roles. Only users with Approver role can "activate" an activity. You can find more about roles here: Users.
Besides that Adobe Target has the concept of Hosts and Environments. You can choose to associate hosts with environments and you can choose to which environments you want to serve saved or approved activities. You can find more about hosts and environments here: Hosts.
As you can see we have quite a few options that allows you to create a workflow in which saved/draft activities can be reviewed in QA or Staging environments and once those are approved promote them to production.