URL is Uniform Resource Locator. In other words, this is a string that identifies a resource on Internet and tells how to communicate with it.
Below is general syntax of URL.
Some popular schemes are http, https and ftp. As a developer you may meet more specific schemas like jdbc and jar. Or maybe you create your own schema, like in some mobile apps, for example fb in facebook application.
# examples of URLs https://socode4.com/articles/en/java/reference/blocking-collections#BlockingDeque file:///path/to/file/filename jdbc:mysql://hostname/databaseName jar:http://www.foo.com/bar/baz.jar!/COM/foo/Quux.class fb://page/myid