What is the difference between mass production and mass communication?

mass production is about production on a large scale.

Mass Communication is about communication among a number of people.

"Mass Communication" is one of those vague terms that could mean almost anything. From the 1950's-80's or so, it would have meant radio and television, or communications systems that reached anywhere from thousands to millions of people when they were broadcasting. It was called "mass" communication because it reached a very large audience. Today, the internet makes it easier to distribute information quickly across the globe, even if it is not likely to reach as many people as the CBS Evening News did back during the 1950's.

"Mass production" refers to a manufacturing process that takes advantage of the economies of scale. Building a factory, buying specialized machinery and training workers costs a lot of money. If you are going to produce millions of copies of a single good, it makes sense to build factories with specialized machines and trained workers that can produce the goods quickly and for a low cost-per-unit. If you are only going to produce a small quantity of a good, you are not going to pay for all of the super-efficient equipment and training. Therefore, the cost-per-unit will be higher.

There is really no similarity between these two concepts, except insofar as they produce a one-size-fits-all product. Mass communication produced programs for a vast audience, and beamed them out across the country. Mass production produces large quantities of the same good and sells them across the world.