A Uniform Resource Locator (URL) is a string instrucing a client how to request a specific resource. They always consist of a scheme (like https) and a scheme specific part (like //www.example.com).
The format of a URL is standardized in rfc1738.
Uniform Resource Identifiers
The term URL and URI are often confused for each other. A Universal Resource Locator has enough information for a client to actually get the resource. This is not always true for a URI. An example of a URI is: