Members of a group have something in common, even if it is only that they are all in the same place at the same time. A team is a group working together to reach a goal - winning the game, solving a business problem, curing cancer, etc.
They use a team or group for delegation of responsibilities
I believe that since we are talking about 1 group (singular) the correct way to say this would be 'A group of horses is called a team'.
Group
a team
The team has won several group awards this year.
Its a team all right.
a team?
Team
A group of oxen is called a team.
Team
take charge in a group of individuals
Team, as in football team.