You can think of groups as 'active care lists'. For example, if you have created a hospital visit group then all the people in that group should be in the hospital. That being said, you are going to be adding and removing people from groups.
Removing a person from a group will not delete any existing updates, tasks and milestones.
Removing People From Groups
Click on the person you'd like to remove from a group(s)
Click Edit profile
Click the 'x' next to the group you wish to remove that person from
Click Save person