Presently, there are specialized rooms with highly technical audio and visual equipment, and wall size two-way mirrors, which can be used for the purpose of conducting a focus group. A very wide range of issues can be addressed in focus groups. Although it is not recommended that the focus group be an exclusive technique in a research project, a wealth of information can be obtained when it is employed. The focus group helps the researcher to understand the attitudes and perceptions that can be influenced by social setting and interpersonal dynamic. A well conducted focus group utilizes interactions to explore topics in more detail and draw out feelings of each participant based on the reaction to what others have stated or exhibited in the group.
Group dynamics help to uncover certain issues and elaborate on others.
If understanding perceptions within a social context is not one of the research purposes, at least secondarily, then the group interview may not be the method of choice. This link will take you to some other terms provided by Mike. These additional references are provided by Mike.