A concert (as in a "concert tour") is a performance in which a musician or many musicians play music together to a group of listeners (called an audience). In the case of a concert of classical music there may be an orchestra. There is often an important visual element to the performance, such as with a rock concert. However, if acting out a story is an important part of the performance, then this is called "musical theater" or "opera" but some concerts have dramatic, theatrical music, with lights and special effects. Informal names for a concert include "show" or sometimes, "gig" for musicians who play in lots of different concerts, with different groups. A concert tour is a set of concerts where the performers travel to different cities or towns.
The performers at a concert are usually raised above the level of the audience on a stage. Concerts may be held in concert halls which are built for the purpose, or they may be held in any other suitable large building such as a school hall, a nightclub, a barn or a large house or castle. Some concerts are given to very large audiences in the open air. They may take place in a field or in a stadium. The music for these “open-airs” is usually amplified by loudspeakers so that large audiences can hear it.
A concert given by just one performer (or perhaps two) is usually called a recital.
A group of concerts in one place or in one area that takes place for several days may be called a "festival". Examples are: The Proms, the Edinburgh Festival, the Glastonbury Festival etc.
Before the days of recording, a concert would have been the only opportunity most people would have of hearing concerts given by groups.
Usually people who go to a concert have to pay an admission charge. The money that is made from the ticket sales will usually go to paying the performing artistes, producers, and organisers. However, there are also benefit concerts where either the proceeds (all the ticket money) or profits (the money earned) will go to charity. Tickets for concerts can often be bought at the box-office of the concert hall or bought online. Sometimes concerts are free.