Blink is a browser engine developed as part of the free and open-source Chromium project. Blink is by far the most-used browser engine, due to the market share dominance of Google Chrome and the fact that many other browsers are based on the Chromium code.
To create Chrome, Google initially chose to use Apple's WebKit engine. However, Google needed to make substantial changes to its code to support Chrome's novel multi-process browser architecture. Over the course of several years, the divergence from Apple's version increased, so Google decided to officially fork its version as Blink in 2013.