There is no difference in functionality between a team admin and a team owner. Owners are usually the functional lead in charge of the team while admins are usually the operations managers who are responsible for supporting that team.
Team owners and admins can do the following:
1) Managing membership of team
Team admins can add or remove members freely. This is done from the settings page next to teams.
2) Visibility of all team deals
Team admins can see all deals (including confidential) from members of their team.
3) Visibility of payments
Team admins can see all the payments from everyone on the team. Team members can only see their own payments.
4) Supporting team users
Team admins can add themselves to any deal activity as long as someone on their team is involved. This allows for supporting users and fixing tags, etc. They must be announced when they do this.
5) Add other team admins
Team admins can add others admins for their team.
6) Add external users
Team admins can add external users to internal team activities.
Teams are typically organized by functional group (eg. an R&D team or a talent acquisition team).