A festival or gala is an event ordinarily staged by a community, centering on and celebrating some unique aspect of that community and its traditions, often marked as a local or national holiday, mela or eid. Festivals often serve to meet specific purposes, especially in regard to commemoration and/or thanksgiving. They are associated with celebration and may also provide entertainment, which was particularly important to local communities before the advent of mass-produced entertainment. These celebrations offered a sense of belonging for religious, social, or geographical groups. Festivals that focus on cultural or specifically ethnic topics also seek to inform members of their traditions and the involvement of community elders sharing stories and experience provides a means for unity among families. A festival is a special occasion of feasting or celebration, usually with a religious focus. Aside from religion, and sometimes folklore, another significant origin is agricultural. Food (and consequently agriculture) is so vital that many festivals are associated with harvest time. Religious commemoration and thanksgiving for good harvests are blended in events that take place in autumn such as Halloween in the northern hemisphere and Easter in the southern. In Ancient Greece and Rome, festivals such as Saturnalia were closely associated with social organisation and political processes as well as religion. In modern times, festivals may be attended by strangers such as tourists, who are attracted to some of the more eccentric or historical ones.