API stands for application programming interface. An API is any way for one application or program to communicate with another one. There are tens of thousands of APIs in the world, many of which are actually built into our programming languages and tools. For example, later in this course you will be writing code that communicates with a MySQL database. The way we will do this is through an API provided by MySQL.
When we talk about APIs in JavaScript, typically we are talking about services that can send or retrieve data over the internet using ajax. Again, there are thousands, upon thousands, upon thousands of open APIs you can use with JavaScript. Most of these use REpresentational State Transfer (REST) for