I think most people use the terms interchangeably, but there is a subtle difference in the two terms that is understood. "Garbage" tends to be more "gross" (rotting food, diapers, etc) and "trash" is more generalized waste (packaging, broken items, etc). For example, someone who most often uses the term "trash" may say "I'm glad tomorrow is trash day. This kitchen garbage stinks, it needs to go to the bin outside". We also use the term "garbage truck" not "trash truck" because it tends to smell and there's all sorts of gross stuff mixed together in there.