What is Group Dynamics?

Legal Definition
Group dynamics is a system of behaviours and psychological processes occurring within a social group (intragroup dynamics), or between social groups (intergroup dynamics). The study of group dynamics can be useful in understanding decision-making behaviour, tracking the spread of diseases in society, creating effective therapy techniques, and following the emergence and popularity of new ideas and technologies. Group dynamics are at the core of understanding racism, sexism, and other forms of social prejudice and discrimination. These applications of the field are studied in psychology, sociology, anthropology, political science, epidemiology, education, social work, business, and communication studies.

There are three main things that can affect a team's cohesion (the act of working together well). They are: environmental factors, personal factors and leadership factors.
-- Wikipedia
Legal Definition
1. Character, ability, opinion, force of will intertwining for development and survival among people with a common objective. 2. Group behavior decomposed into principles as a field of study.