Let's say, just for the sake of illustration, you want to find everything on On the Way! regarding Sherman tanks.
First you try a search with M4 in the search box and get a list returned, but then notice that other Sherman variants are not listed, for example M4A1s. Well that's because of the way the Freefind and many other search engine work.
Your original search for M4 will only return results where the exact phrase/word M4 is in an OTW page, which will be any thing with spaceM4space. All the others, such as M4A1 and M4A2 are not listed. That's because M4A1 and M4A2 do not match M4.
So to get all of the On the Way! pages about Shermans, you'll need to modify your search above to look something like this:
m4 m4a1 m4a2 m4a3 m4a4 m4a5 m4a8 sherman firefly
Now that returns many more pages and gives you a better chance of finding what you're looking for!