DLC stands for Downloadable content. It's a way to extort another $60 from players for bells and whistles that should have been in the original game in the first place.
Anyone remember the days when 300+ hours of content was considered more than 12 times the content of the average game? Those were the days. Way back in last week.
DLC is basically a way for developers to release
additional content that's too small to qualify as an expansion but too big to let it be patched in for free.