URL it's the address of a resource available on a network, be it the internet or intranet network, and it means in English Uniform Resource Locator, and in Portuguese it is known as Standard resource locator.
In other words, url is a virtual address with a path that indicates where the user is looking, and it can be either a file, a machine, a page, a website, a folder, etc. Url can also be the link or address of a website.
A URL is composed of a protocol, which can be either HTTP, which is a communication protocol, FTP, which is a quick way to transfer files over the internet, and so on.
The format of URLs is defined by the RFC 1738 standard.
URL shortener
A URL (or URL) shortener shortener, in English) is a tool that compresses very long links. Sharing very large links can be a problem, and for that reason, content dissemination online it's easier when the links are shorter. There are several tools that work as URL shorteners, like TinyURL, Bitly, Goo.gl, etc.
