What is the name of the character played by John Ventimiglia?

The character played by John Ventimiglia is Artie Bucco.

Arthur “Artie” Bucco Jr. is a restaurateur and chef in The Sopranos. He owns and runs Vesuvio, later Nuovo Vesuvio, with his wife, Charmaine. Unlike Tony Soprano and most of their associates, Artie is not a made member of the Mafia. His long friendship with Tony repeatedly pulls him close to the criminal world, even though he generally tries to remain a legitimate businessman.

John Ventimiglia played Artie throughout the series, appearing from the first episode through the penultimate episode. Ventimiglia's performance gives Artie a distinctive mix of ambition, insecurity, comic frustration, and genuine affection for his friends and customers.

Viewers may confuse Artie with Patsy Parisi, Paulie “Walnuts” Gualtieri, or Silvio Dante because all are recurring men in Tony's circle. Those characters are mob figures played by Dan Grimaldi, Tony Sirico, and Steven Van Zandt respectively. Artie's restaurant also serves as a recurring meeting place, making him closely connected to the mob without becoming one of its soldiers.