Let's say you're doing some research on the Internet and your not having any luck finding what you're looking for.... later you try using different keywords and were able to find what you needed. What quite often happens with me is my search search queries will become more accurate as my research progresses. The purpose of a bridge post is to make a page/post specifically for other people out there who are starting out on the same branch of research that leads them directly to the answer you found.