A uniform resource locator (URL) is way to identify the location of resources such as files on the Internet. URL syntax combines domain names with file pathways and protocols needed to retrieve the files.
URLs are a subset of the more generic uniform resource identifier (URI). As a practical matter, the term URL is frequently used when URI would strictly be more correct. Also, sometimes URI is used when many would expect to read URL. For most technical purposes, the differences between URLs and URIs are not significant.
URL can also mean universal resource locator. There is no practical different between the two different interpretations of URL.
See: RFC 3986