The dictionary definition of synchronization states that it is a process of coordinating two or more activities at a time. These activities can be anything, such as various instruments playing various tunes in an orchestra or the different parts of an automated assembly line in a car factory.

As far as test automation goes, synchronization is the process of matching the speeds of the application under test and the testing tool, which in this case is Selenium. Synchronization in Selenium WebDriver is implemented using something called a wait.