A concert is a live performance (typically of music) before an audience. The performance may be by a single musician, sometimes then called a recital, or by a musical ensemble, such as an orchestra, a choir, or a musical band. Concerts are held in a wide variety and size of settings, from private houses and small nightclubs, dedicated concert halls, entertainment centres and parks to large multipurpose buildings, and even sports stadia. Indoor concerts held in the largest venues are sometimes called arena concerts. Regardless of the venue, musicians usually perform on a stage. Before the dominance of recorded music, concerts would provide the only opportunity one would generally have to hear musicians play. Informal names for a concert include "show" and "gig".
Being a fan of groups such as KISS, I'm used to over-the-top, pyro-laden concerts and love them as such. However, some of the best concerts I've ever been to were small, intimate performances where a band or bands performed tunes acoustically or in very small venues. Shows like that are more "experience" than "performance" in my book.