Committees
Committees are workgroups led by a volunteer chair that have ongoing assignments.  For example, FPA has an Ethics Committee.

Councils
Councils are typically set up around a specific constituency of members — chapter leaders, international members, corporate members, etc.

Task Forces
Task forces are formed to discharge a specific, time-limited task. Examples include the FPA Retreat and Annual Conference Task Forces.

Workgroups
Workgroups are formed for the purpose of ongoing advisory input in a functional area. One example is the Membership Advisory Group.