Is selling concession selling commission?

Yes a selling concession is a selling commission of sorts. The difference is that in an initial public offering the securities are initially bought by the participating brokers at a discount and then immediately resold for the full amount. This spread is called the "selling concession". Although the terms are used interchangeably, a commission is associated with a broker where a concession is associated with a dealer. The difference is wether the agent in the middle uses his own money (dealer) or someone elses money (broker).