The Teams allows you to select the list of people to whom you want to assign the tasks. You will have access to the teams to which you are the team lead, and the users that are assigned to the same teams are assigned to.
Click here to know more about creating teams and assigning it to users.
Once the teams are created and assigned it to the users. You select the teams from the Project Hub page, and you see only the users related to the teams that you have selected for assigning the Tasks.