Application Programming Interface (API)
An API defines how to use another piece of software. The API shows you the public functions and data you can use with your own software, allowing you to do more with less code.
Uniform Resource Identifier (URI)
A Uniform Resource Identifier (URI) is a string of characters that unambiguously identifies a particular resource. To guarantee uniformity, all URIs follow a predefined set of syntax rules, but also maintain extensibility through a separately defined hierarchical naming scheme (e.g. "http://").
Uniform Resource Locator (URL)
A web page and the images and videos it contains all have their own URL, a specific address where they can be found on the Internet.
A URL is a specific form of URI for web pages and the content that they contain.