Though there are very specific and technical nuances, you can typically think of an API (application programming interface) as something that facilitates a two-way connection between applications—say, a CMS and third-party analytics tool—to accomplish any number of tasks: fetching data, pushing data, and the list goes on. A webhook is an API pattern; therefore, it becomes difficult to compare and contrast the two in a traditional way. For practical purposes, consider a webhook as a simple API that pushes data from one system to another without serving any other function.