On a Drupal site, one uses a lot of images and files... The name of these files is the same on the server as on your computer. Not always good to keep it simple.
This module can rename while uploading.
An example..storing the files in a folder 'mytest' with the name picture.???
These are the default settings.
One can use tokens. You see that one can rename and move the already uploaded files!
When using multiple files in one folder, Drupal never overwrites the existing file, but makes it _0, _1, _2,..
You don't see it in the upload interface, but the name is different.
An example. In stead of chaos, one knows which image belongs to which content type.