It's like the blind leading the blind. Most people don't know what halal is, but they know they're against it.
All foods are labelled halal if they are, so you can clearly see if a certain food is or isn't. The broader definition of "halal" for muslims is something which is allowed. So this could be drinking clean water or watching a certain TV show. When it comes to meat, it means that the animal was slaughtered in regards to a certain procedure. The procedure is something along the lines of the animal should be quickly slaughtered via the neck and the blood to be drained. This originates from preventing blood from pooling or using sick animals, which can result in diseased meat.