What does it mean, “Enhanced with up to fifteen percent chicken broth”?
It’s what you use to make the fecal soup.
It means that chicken broth has been added to it as an “enhancement,” and that up to 15% of the weight is added water.
Poultry supplier have been adding salted water for years, ostensibly for benefits in taste and shelf-life – but the main benefit is that you’re making the chicken heavier and it’s sold by weight.
After labeling laws required disclosure of this, chicken broth became the additive of choice, because it’s more euphonious than “water.” (Of course, the cost of chicken broth is trivial in comparison to the price of chicken meat.)
“Enhanced” is just a legally acceptable way of blowing smoke up your butt.
“Enhanced with chicken broth!” sounds more like a selling point than “Water added.”
I was afraid of that.
Yep, it’s something that I’ve been struggling with for years. In my alternate life, I’m a cook. I’d guess that I smoke right around 200 pounds of pork, chicken, fish and beef for parties and get-togethers…every month. On one hand,having someone brine your meat for you helps keep it moist and tasty, on the other…I’m paying upwards of $3.00/lb for water added to the meat!
Brining is a natural topic for people who BBQ quite a lot…paying someone else to do it is close to a sin! 
When it comes down to it, I buy my meat from a butcher and if it needs brining…I do it myself. When I’m faced with a BBQ emergency, I’ll buy the enhanced meat…it’s usually a TIME issue.
-KN
Is that anything like koshering with salt to remove blood?
Brining tricks the meat into taking on more water than it already has. Each cell has a membrane that’s semi-permeable (it will let some things pass through, but not everything.)
The following is paraphrased, and the info credited to Mr. Brown, so we’re not in copyright trouble.
Alton Brown, in I’m Just Here For The Food, likens the membrane to border guards that try to maintain balance between the inside and outside of the cell. If you soak a chicken breast in plain water, there’s no salt outside the cells, but there’s some inside. So, the membrane allows some some water to move into the meat and some salt to move out into the water. So, the meat loses some of its native flavor to the water.
If you soak the chicken breast in salted water, though, there’s more salt outside the cells than inside, so the membrane allows salt into the cell to try to achieve balance. However, the extra salt needs more water for balance, so the membrane allows more water in, too. After 8 to 24 hours in the brine, the meat is perfectly seasoned with salt and puffed up with more water than it had before. If your brine had other flavors mixed in, they also have passed into the cells.
So, the brined meat is tastier, and the extra water means it is more forgiving of overcooking.