This process used to rename multiple files that will have the same file names. Two files in the same folder cannot have the same file name. So, that, Windows will add a number to the at the end of the file names. You can easily rename the multiple files at once.
It will appear that you will rename only one file. Whereas, this is the base name of the file. Once you type the name, you can hit the enter button.
You can see the base of the file name is one that you rename and then, Windows will add a number to the end of each file name automatically. SO that, it can be easier to sort whenever you want. If you want to rename the multiple batches of files, you can repeat the same process as many as time as you have different base file names.