A committee is a group of people that come together to do something or decide something. It is often part of a bigger deliberative assembly. A committee might have a special job to do for a specific topic.
A deliberative assembly may create a committee (or "commission") that has one or more persons to help with the work of the assembly. For bigger organizations, a lot of work is done in committees. Committees can be a way to get people together that have similar experience from different parts of an organization. Without the committee, these people might not have a good way to share information and work together.
When a committee is created, a chairman (or "chair" or "chairperson") is chosen for the committee. Sometimes a vice-chairman (or similar name) is also chosen. The committee chairman often organizes the meetings.
When the committee finishes its work, it gives the results in a report to the larger group. The report may include the methods used, the facts found, the conclusions reached, and any suggestions.