Application programming interface (API)
An application programming interface (API) is a communication system that allows two applications or platforms to “talk” to each other. Social network APIs allow these platforms to integrate with other software providers and apps. For example, Hootsuite uses Twitter’s API to publish tweets, and Instagram’s API to schedule posts.
When Instagram wanted to shut down the shady “growth-hacking” apps people were using to grow their audience artificially, they shut down their old API and launched a new one with much tougher privacy controls.