When using the forum search option, done by visiting the Search button found at the top menu bar of the forum you're visiting, there are a couple of different ways to have your search results display depending on what you're looking for.
Once you have filled out one or more of the search options on the search page, at the very bottom of the page you'll see one last option for "How to search...". This gives you the options for "display results as posts" and "display results as threads". If you choose the "display results as posts" option, after you click the Search button the search results will display you individual posts that contain the items that you are searching for. This view is best used if you're trying to find a specific post that was made on the forum. Otherwise if you're just wanting to find a topic rather than a specific post, use the "display results as threads" view option. When this is selected, the search results you get back will list out the individual discussion topics from the forum that has content which contains the items that you are searching for.