When you have a program code, or supplementary pdf files which support your published paper, you may want to upload them to a web-site and announce its URL in public. However, in most cases, by many reasons, those URLs will have to be changed. In that cases, you need to update the already announced URL, but how to update those anonymous public?
Well, this is the motivation to get a persistent (or, permanent) URL, which is in fact just a representive URL and this URL will forward those visitors to the actual URL that you register and may change in the future. One example is the well-known DOI (https://www.doi.org/).
Now, the question is, can we do this for other resources? A useful answer is to use www.purl.org.