"Selling" is simply informing people of the availability of one half of an economic exchange. Putting a notice up that says "Sofa, $50 ONO" is no different than putting a notice up saying "will pay 50$ for sofa".
"Advertising", on the other hand, attempts to persuade. It endeavours to use psychology to create a transaction when one would otherwise not have taken place. It's a sign that says "Sofa, $50. Incredible value!!". This is not ethical because if we assume that the market would have converged on the correct price in the absence of advertising, then advertising distorts the market and makes it less efficient.
Note that unadorned "buying" and "selling" are mirror counterparts, but there's no buyer's counterpart to "advertising". This is because the value of money is well known and non-negotiable, while the value of the good or service is subject to influence. This is an inherent bias that always works in favor of the selling party.