A brown bag seminar, session or lunch is generally a training or information session during a lunch break. Brown bag is a symbol for meals brought along by the attendees, or provided by the host. In the USA, those are often packed in brown paper bags. Brown bag seminars normally run an hour or two.
The aim is to use regular breaks, e.g. the lunch break, to provide some information to the attendees in a voluntary and informal setting. It is often followed by a discussion of the topic. These sessions are common at universities and private companies. They are an interesting medium for knowledge management and internal communications.
In universities, especially for graduate students, brown bag seminars are often offered to update the researching community about ongoing research. Usually held by schools, universities and governmental institutions, they involve lectures, presentations, or talks by researchers, mostly professors about their ongoing research. Professors may visit from other universities to talk about their research.