The word premiere (or première, from the French première, "first") generally means "a first performance". This can refer to plays, films, and so on. Premieres for theatrical, musical and other cultural presentations can become extravagant affairs, attracting large numbers of socialites and much media attention. Standard trappings may include a parade along a red carpet. At a festive film premiere the main actors involved in the performance may attend.
"Worldwide" premieres (or "world" premieres) mark the first showing of the performance ever; regional or national premieres may signal the first performance/screening in a given country. A film may screen at a film festival before its general release to movie theaters.
Betts (2004: 12) attributes the introduction of the film premiere to Sid Grauman.