Jenkins is an open source automation server used to automate the repetitive tasks involved in the software development process. It is used to automate the building, testing, and deployment of software applications. For example, Jenkins can be used to automatically build and test a software project every time a developer commits a change to the source repository. Additionally, Jenkins can be used to monitor the execution of externally-run jobs, such as cron jobs and procmail jobs, and can even be used to set up a continuous delivery pipeline.