Easy answer the most efficient way to sell your product in the market place
In the United States, in corporations, "Sales" means the department that actually performs sales transaction.
I used to work at a laboratory that bought $200,000 minicomputers. I would call the computer company's sales department and speak to a salesperson. The salesperson would try to guess how many computers we were likely to buy, how good a customer we were likely to be, how serious our interest was. The salesperson would try to "close the sale," convince us to agree verbally to buy the computer. The salesperson had the authority to decide what price we would pay. The catalog might say $200,000, but the salesperson might offer us a 20% discount in order to close the sale. The salesperson might decide to treat us to lunch to discuss the deal.
"Marketing" meant the department that communicates with the public, decides what advertising to run and where to run it, decides what the "marketing message" (central theme of the advertising) should be.
Marketing might decide to sponsor a race car driver in return for having the company logo visible on the side of the car during the race. Marketing might decide what things to brag about: price? speed? versatility?
The salesperson might send us catalogs, brochures, and other materials to help convince us to buy the computer. Those catalogs and brochures would have been created by the marketing department.
Selling, pushing, promoting service or goods to the market. (my words)
The commercial processes involved in promoting and selling and distributing a product or service (dictionary)
Marketting is the abilities to manage associated tasks at the same time such as: how to sell a product, promote the your current products, increase the entire profit, create a new market for the current produts, improve the current products to satisfy your current customers, gain new customers, perfectly concounter the competitors, and studying the behaviors of the customers, and the competitors.