I had a look into a program's folder in Program Files of the Windows directory and I found that it has a lot of files with .db extension. I opened one with notepad and I saw that the first string in the file is sqlite 3. What is the difference between files ended with db and those with sqlite extensions ?
There needn't be a difference in the file format. File format is totally unrelated to the extension it is given. For good practice, we all agreed they should match so that we can identify files and their formats by their extension.
However there is nothing that will keep developers or users from using deviant extensions for established file formats.