1) A group is defined as two or more interacting individuals who share common goals and perceive themselves as part of the group, while group dynamics studies the interactions and processes within groups.
2) Key features of groups include having at least two members who interact, develop leadership, have a collective identity, establish group norms, and ultimately find satisfaction from group membership.
3) Group development occurs in phases including forming, storming, norming, performing, and potentially adjourning for temporary groups, as the group establishes structure, roles, and becomes functional in accomplishing its goals.