Events (or system events) are identifiable occurrences or changes that happen in a business system, such as a database or an application. An event in business technology could be an action, such as making a change to a file or removing a record from an application. Events can be monitored and set to trigger an action when certain criteria are met. Software that changes or performs a task when responding to an event is regarded as event-driven or event-based.
Event-based programming typically involves a relatively small amount of activity and is triggered by some action, also known as an event, occurring. In an event-driven application, the flow of execution is defined by a user event, such as clicking on a file or queries in a database search. While these events may seem simple, they form the basis for serving users with quick, accurate responses that provide a better user experience. After all, software development at its core is all about helping to produce more intuitive products for end users.
A practical example of an event being used in event-based programming might be an employee requesting PTO in a system. When this employee submits their request, this would trigger a notification being sent to their manager for them to approve. The manager could then view the details of the request, approve or reject the request, and it would be updated in the system without any additional logins required.