What can you compare the forum to in modern society?

It depends. The Romans had two types of fora (plural of forum): the forum civilium and the forum venalium. The former was the civic forum and the latter was the commercial forum, or market. The forum civilium was the civic centre and the heart of a city and its public, political, judicial and administrative life. It was comparable to a city centre. It had a comitium, the place where the popular assemblies met to vote, public speeches were made and public debates were held. It had a senate house. Roman towns had their own local senate, modelled on the senate of the city of Rome.