A citizens' assembly is a group of people representative of the voting population, typically between 50-200 people, selected to deliberate on important public questions decided by the Government and provide binding recommendations on public policy.
It is formed ad hoc by the government and is provided with time, resources, and a broad range of viewpoints to learn about the issue.
Typically, invitations to join the assembly are random, but devised enough such that sufficient diversity is achieved. For example, Ireland convened a 100-person assembly to deliberate a constitutional amendment to legalise abortion.