Downloadable content is additional content that is released for video games that are already on the market, for an additional fee. This content usually includes new maps, new guns, new activities and the price could range anywhere from $10 to $40.
The issue people seem to have with this is that they claim video game companies are shipping out "half completed" games and saving most of the content for DLC packages so that they can charge more money.
Let's take an example of DLC, so that we can bring this scenario to life: Destiny. Destiny is one of the games who has received the most flak for being money hungry in their sales models related to DLC. Destiny released on console on September 9th, 2014 and has already released 2 downloadable expansions with another one slated for this September of 2015. You were able to buy the first 2 expansions, both for $30. Each expansions came with tons of new guns, maps, and activities as well as a higher level cap.
People don't seem to realize the way video game production and marketing works. Video game developers like Bungie (responsible for Halo franchise, as well as Destiny) are obligated to keep their staff working on projects and content. If they don't constantly put out content, they go out of business. Or do you think once they finish developing the game, all the employees get the summer off from work so that they can go home binge on the games they created? No, they don't. They still need to get paid and therefore they still need to work. See how it works?
For years, PC gaming dominated console gaming in the sense that PC games received continued support and expansions - something that console gaming wasn't yet able to achieve, due to lack functionality on the consoles. Now, developers can fix bugs and glitches with the game after launch as well as make tweaks to improve the experience for their customers. We should be thankful for this capability and the features it brings with it.