The words 'group' and 'team' are, for the most part, interchangeable - at least most people use them that way. But there are distinct differences between groups and teams. For example, we have a football team, not a football group - or we have a special interest group, not a special interest team. While the differences are subtle, they are indeed different, and we need to understand what those differences are.
The main difference is that a team's strength or focus depends on the commonality of their purpose and how the individuals are connected to one another. On the other hand, a group can come from having a large number of people or a cohesive willingness to carry out a focused action - political reform, for example.
While these differences might be subtle, we have to understand that a group is a number of individuals forming a unit for a reason or cause, and a team is a collection of accomplished people coming together for a common goal that needs completion. The subtleness of these differences are more pronounced when we take these words a step further and look at a work group and work team.