A concert is an in-game concept where Sims play or listen to music performances.
The Sims 2: University
The community lot Little Fallorayne Amphitheatre in Académie Le Tour in The Sims 2: University features a stage for impromptu concerts by 1-3 Sims.
The Sims 3
in The Sims 3, stadium rabbit holes have a chance of holding concerts on Friday and Saturday nights. A Sim can attend the concert inside the stadium. The concert lasts around 15 in-game minutes, improves the Fun motive, and gives the 
"Saw Great Concert" moodlet.
Theater rabbit holes have a chance of holding concerts or symphonies on Friday nights. A Sim can attend the concert inside the theater. The concert/opera lasts longer than the stadium concerts, but has the same effects on the Sim.
A Sim in the Music career level 6 in the Rock Branch (Lyricist) or higher can perform concerts at theaters.
The Sims 3: Late Night
2-4 Sims can form a band in The Sims 3: Late Night, which can allow them to receive opportunities to host concerts on certain eligible lot assignments if the lots have 4 or more eligible instruments (Any combination of guitar, bass, drums, and/or piano) on them. A one-off concert in a stadium is also the final mission of the Band opportunities.
A Sim can also hold an impromptu solo concert on a public space or inside a subway station.
The Sims 3: Showtime
A Sim in the Singer career can host concerts on eligible lot assignments (Primarily parks and Showtime-type venues) if they have a show stage on them. The Sim can optionally choose to bring a guitar and/or some show stage props on the stage and use them in the concert performances too.
SimFests have a relatively high chance of having NPCs perform Singer-type concerts, provided that any NPCs in the town are high enough in the Singer career to be selectable for a SimFest.
A Sim who has practiced on DJ booths a lot can receive opportunities to host DJ performances, regardless of which career they have. The lot eligibilities are the same as those for Singer gigs.
The Sims 3: Into the Future
The Sims 3: Into the Future encourages Sims with a Laser rhythm-a-con instrument and its related skill level to host impropmtu solo concerts on public spaces for other Sims to watch, especially for the "The Lustrous Entertainer" Legacy Statue challenge, and several community lots in Oasis Landing feature tiny stages with one laser rhythm-a-con and one guitar.
No formally assigned concerts are available, however. There were plans during the development of Into the Future to allow laser rhythm-a-cons to be used in Late Night-type concerts, but the feature was cut before Into the Future's release, and there are no known ways to re-instate that feature.
The Sims 4
The The Sims 4 base game festival "Sims Sessions" took place from June 29 - July 7, 2021 at the Magnolia Blossom Park in Willow Creek, featuring in-game performances by real-life artists such as, but not limited to, Bebe Rexha.