A commission has powers delegated from above to it and is given a task to perform (e.g.: a procurement commission, the Securities & Exchange Commission). Its terms of reference are relatively specific, even though these may be very broad (e.g. European Commission) or very narrow (a company's IT procurement commission). Representativeness is not a relevant criterion for a commission.

A committee is a more horizontal grouping of appointees for co-decision making. (Project steering committee, monitoring committee, special parliamentary committee, village fair prize committee, strike committee). The emphasis is more "how are we going to do this?". Committees operate according to formalised rules of procedure. If you are unsure whether to use committee or commission, use committee.

A panel has no powers, and will simply advise a decision-making body. It is usually composed of experts who may be external to the organisation of the decision-making body. Members should be chosen on the basis of their expertise. Representativeness is not a relevant criterion.

A working group is conceptually similar to a committee, yet more informal, temporary and ad hoc. Its members are the people actually working on the thing that is the subject of its decision-making. The decision-making is more detailed (e.g. there is a problem with xyz design component, so let's delay production of abc until ...).

A board is supreme, i.e. it is not subordinate, i.e. it does not receive instructions, but instructs the executive to do things. (e.g. board of directors in a company, board of trustees, board of governors)

A council is a body of members who are representative of a larger group (typically an electorate). Its decision-making and powers are not relevant criteria. The criterion is solely that it is representative.

A roundtable exists solely to exchange information through question, answer and discussion among its members. Attendees may be heads of government, journalists, company heads, high-ranking officials. While heads of government may reach agreement around a roundtable, this decision-making is not the relevant criterion for calling the meeting a roundtable. Roundtables are often not recurrent.

A group (e.g. a G7 meeting, group of wise men = monetary policy experts) is used when there is the need to emphasise equality between members. Its members are independent and not subordinate to any decision the group. The group is not a body having any authority. Agreements may be made, but the emphasis is more on discussion.