A Forum was the main center of a Roman city. Usually located near the physical center of a Roman town, it served as a public area in which commercial, religious, economic, political, legal, and social activities occurred. Fora were common in all Roman cities, but none were as grand as the fora of Rome itself.
A forum is not unlike a Greek Agora in concept and even design somewhat. It is likely that there was some Greek influence on the concept of a public gathering place for the Romans. In fact, a Roman forum often included certain physical aspects of a Greek agora, such as the use of porticoes. However, where an agora was maintained as an open public place in a Greek city, Roman fora developed into much more, with greater purpose and use. They were filled with shops, porticoes, temples, offices, and triumphal arches; and they were where important civic and political announcements were made, as well as where the less tasteful aspects of Roman life occurred, such as prostitution. As the years of Roman history passed, the fora of Rome became quite enclosed, and probably very crowded and chaotic.
The main forum of the city of Rome was the Forum Romanum. Its placement in the central part of the city dates back to the time of the Tarquin kings, and it was seen fit to build a sewer, the Cloaca Maxima, to provide proper drainage of the marshy land between the Esquiline, Capitoline, and Palatine Hills down to the Tiber River. With the land properly drained and dry, this area naturally became a central gathering location for the Etruscan inhabitants. When the Roman Republic came to be in 509 B.C., this area retained its public use, and was where processions and elections took place, and eventually where the Roman Senate gathered.
While the Forum Romanum was the main forum of Rome, there were several other fora located throughout the city. Each of these fora had a specific purpose unto themselves. These included the Forum Boarium (the cattle market), and several Imperial Fora. Roman Emperors such as Augustus and trajan built the Imperial Fora, usually with the spoils of war, in order to celebrate themselves and their victories.