If you are a subscription owner of a number of licences, you may be familiar with the 'Manage Users' option under your subscription from the 'Options' panel on your left toolbar.
When you click on the black "pencil" icon next to a member's name, you'll be brought to a page where you can edit subscription rights and channel rights (as shown below).
Subscription Rights allow the member the same rights as the Administrator of the subscription, giving them the ability to manage members and access the shared contact list of the subscription. Members with subscription rights may also add or remove members.
Channel Rights allow the member the same rights as the 'channel owner' of any channel they are added to, given that the owner of the channel is within the same subscription. As the channel owner, members with channel rights can manipulate the channel, such as extending expiration dates.