Lando Calrissian is a fictional male Corellian in the Star Wars series. The character was portrayed on screen by Billy Dee Williams. His allegiance / loyalty is to The Rebel Alliance. Lando Calrissian, from his first appearance in the 'Star Wars V - The Empire Strikes Back' to his (current last as of June 2013) last in Star Wars VI - Return of the Jedi.
Lando Calrissian is seen as one of the most important characters of the original trilogy. He has not appeared in the first two Star Wars sequel movies, rather sitting these out. His character has just been written out, he's not adverse to coming back, he said he would like to if they wrote him in.BND
There had been a rumour that Finn, one of the new characters in the movie is rumoured to be the son of Lando Calrissian. There's no connection between Finn and Lando as yet, unlikely that there will be one.
Lando first appears as the Administrator of Cloud City, Bespin and is an old time friend of Han Solo. Han won the Millennium Falcon off Lando in a game of Sabacc which is not explained in the movies, just the expanded universe,
Lando invites his guests (Han Solo, Princess Leia, Chewbacca, C-3PO, R2-D2) to dinner but it is a trap as Darth Vader is waiting for them. Vader had arrived earlier on the planet. Vader tells Lando that all he's interested in is Luke Skywalker and its really a trap for him.
Darth Vader planned to freeze Han Solo in frozen Carbonite and send him to Jabba, the Hutt. Vader agreed to leaving Leia, the droids and Chewbacca with Lando but Vader changes his mind at the last moment and plans to take the Princess with him. Calrissian orders the evacuation of he Cloud City to use as a cover to free Han Solo's friends from the Empire.
Lando with the assistance of the Cloud City security frees Princess Leia, Chewbacca and the droids and they escape using the Millennium Falcon picking up Luke on the way.
Lando has managed to get a job as one of Jabba the Hutts' guards where he helps or at least tries to help rescue Han. During the fracas on the sail boats over the Sarlacc Pit, Lando falls into the pit and has to be rescued by Han Solo and Chewbacca.
At the Rebel base, Lando with the help of Nien Nunb agrees to lead the space ship assault on the new Death Star using the Millennium Falcon. The only other person to have destroyed a Death Star is Luke Skywalker. Where as Luke fired a single shot down a chute, Lando Calrissian has to fly into the unfinished Death Star and destroy the main energy source for the station.
Lando makes a guest appearance in one of the cartoon series episode's where he persuades the crew of the Ghost ship to give him a lift, after Lando has won the Rebel's astromech droid. Lando leads the crew of the Ghost ship from one situation to another until they finally reach his ultimate destination and at which point he departs until they meet again...
You can't have a Han Solo back story without featuring Lando Calrissian, Han's long time friend. Lando is to be played on screen by Donald Glover, an American actor, singer and D.J.. The film will probably show how Han Solo won the Millennium Falcon off of Lando.
The trailer that has been released doesn't give too much away. It does give the impression that Lando will have a substantial role to play in the film and not just as someone who Han Solo wins the Millennium Falcon off in a Sabacc card game.
The Battle of Tanaab is mentioned in Return of the Jedi and gets Lando Calrissian a promotion to General in the oncoming battle. Tanaab is only detailed in the expanded universe. Lando Calrissian took part in the Galactic Civil War when he took on a group of pirates in orbit round the planet of Tanaab.