OMG! It's amazing! Michael Bearden really is a multi-talented artist: he can play keyboards, sing, be a musical director, model for hip shades, hand-paint and mime... Peekaboo!
(sorry! couldn't help it!)
golittleperson: sold-out simply means that ALL the tickets were sold before the show begun.
If the capacity of the venue is 700 people but the promoter puts only 600 tickets on sale for whatever reason and the 600 tickets are sold then the show is said to be sold-out.
In some countries there's a law that obliges the venue to sell a certain number of tickets the very day of the show, just a couple of hours before it starts.
Although all the tickets are sold, you can always see empty seats in a venue because there's always a percentage of ticket-holder who don't show up. And sometimes a venue is half empty because of a major bummer like a public transportation strike which makes it impossible for hundreds of people to go to a show. Especially here in Europe where fans are used to follow bands from one country to another and special packages are sold by tour promoters and bus companies.
Did I answer your question?
Now sold-out or not has not influence on the quality of a show anyway so who cares?