What are the membership and duties of the Greek popular assembly?

The members were the citizens of the city-state. Depending on the franchise, it included all males (as in the extreme democracy of Classical Athens) or in some cities there was a property qualification to be able to attend and vote (as there was also earlier in Athens). Their duties (or should we say privileges) was to vote on motions put before them at the assemblies. All legislation had to be approved by them.