Short answers, pulled from the story.
Billy Dee Williams portrays Lando Calrissian in The Empire Strikes Back, Return of the Jedi and The Rise of Skywalker. Donald Glover plays a younger version of the character in Solo: A Star Wars Story and is expected to reprise the role in another film currently in development.
Lando Calrissian was introduced in The Empire Strikes Back in 1980 as the administrator of Cloud City. He returned in Return of the Jedi in 1983, and later appeared in Solo: A Star Wars Story in 2018 and The Rise of Skywalker in 2019.
Lando Calrissian betrays Han Solo to Darth Vader because Vader threatened to put Cloud City under direct Imperial control if he refused. Lando later helps Han's friends escape Cloud City and joins the effort to rescue Han from Jabba the Hutt.
Fans translated the Aurebesh lettering on Lando Calrissian's cane in The Rise of Skywalker as Landonis Balthazar Calrissian III, a reading the film's writers later confirmed as his full name. An official reference book states the cane's text reads Baron Lando Calrissian.
Jonathan Kasdan, a co-writer of Solo: A Star Wars Story, stated that Lando Calrissian is pansexual. Donald Glover, who plays the character, responded, "How can you not be pansexual in space? There's so many things to have sex with."
George Lucas envisioned Lando Calrissian as a suave con man with the elegance of James Bond and the wit of Star Trek's Spock, designed as a foil to Han Solo. Lucas also considered making him a clone from a ruling clan, an idea never used onscreen.
Yaphet Kotto was considered for the role of Lando Calrissian before Billy Dee Williams was cast. Williams later said the character's cape and surname were interesting things to build a performance around.