"Number 6" the records aren't indexed.If you know much about online records (genealogical or not) you may easily understand the difference indicated by the terms "online records" and "online databases." If you don't perceive any difference in those terms, learning the difference may help you perform better online research.
Most genealogical records were created offline (obviously). When they are put online there are two main formats, images or databases. The exceptions are usually transcribed or abstracted records posted by individuals on their own websites (including blogs) or on websites like US GenWeb Archives. In some cases, these are still databases but the important thing for this discussion is understanding an image versus information typed online.
Databases vs. ImagesDatabases and other typed information (not images) are searchable. The five reasons Michael J. Leclerc's article covers discuss many of the issues you may have with searchable records. I have only seen two ways to search online images of genealogical records. One is OCR (Optical Character Recognition). This method (currently) only works on typed records like books or newspaper records. The computer, in essence, reads the document looking for the search terms you have entered. This technology keeps improving but still has issues with poor quality images. You're probably familiar with OCR if you have searched a large online newspaper database or searched books through websites like Google Books or Archives.org. Poor quality is more likely an issue for newspapers as they are more fragile than most books chosen for digitization.
The second way to search online images is via a database. The database is the index for the image collection. If a database hasn't been created then the images are often referred to as "unindexed." If this is news to you, you may have been missing out on many useful online records.
Unindexed RecordsThe largest collection of unindexed "genealogical" records is probably found through FamilySearch. Most other large genealogical websites only post records once they are indexed. However, you may also find large collections from public repositories like archives and universities or even large private collections so search out digital collections for the locations or topics you are interested in.
If you have only used FamilySearch by using the search form, you are missing out on most of the records. There are millions of images in even one unindexed collection. There are probably hundreds of unindexed collections or partially indexed collections. And, yes, there are partially indexed collections.
When using FamilySearch, you should browse to the list of available collections for your location of interest.
Don't Overlook the Description!Click on the collection you are interested in and read the description.
This will give you invaluable information about what should be included in the collection, whether it is indexed, partially indexed, or browse-only and whether it is complete (i.e. will they add records later requiring you to come back and check the collection again). Once you get used to doing this you will get a lot more from FamilySearch than you ever did using just the search form. Be aware that browsing images may be an option for any website and keep an eye out for collections that might not be searchable or maybe not be searchable by the terms you need to use.
I've added a video showing how to do this, as well.