Open mic

An open mic or open mike (derived from the expression "open microphone") is a live show at a coffeehouse, nightclub, comedy club or pub where audience members who are amateur performers are given the opportunity to perform onstage. Typically, as the name suggests, the performer is provided with a microphone which is plugged into a PA system, to make the individual's performance loud enough for the audience to hear. Often the performers sign up in advance for a time slot with the host or master of ceremonies, typically an experienced performer or the venue manager or owner. The master of ceremonies may screen potential candidates for suitability for the venue and give individuals a time to perform in the show. These events are focused on performance arts like poetry and spoken word, music (often singer-songwriters who accompany themselves on guitar), and comedy. Less commonly, small groups, such as a small rock band duo/trio or a comedy duo may appear. Group performances are uncommon, because of the space and the logistics of loading in and soundchecking such a group.

Open mic nights may have no cover charge, or a very low cover charge, although the venue may have a gratuity jar or "pass the hat" for donations. Venues that have no charge make revenue from selling alcoholic beverages and food. The performers are not typically paid, although the venue may recompense the performers with a beverage or meal. The host or MC, as an experienced professional, is usually paid for her/his services. The host or MC may perform at some point during the evening, either a full set or to fill in when an amateur member is not available for her/his slot. Open mic events are somewhat related to jam sessions, in that in both cases amateur performers are given the opportunity to sing or play instruments. The difference is that jam sessions often involve musical ensembles, possibly even a house band or rhythm section and a jam session may involve the participation of professional performers, especially at a high-end jazz club.

...
Wikipedia