What is Jenkins? The CI server explained
Jenkins offers a simple way to set up a continuous integration or continuous delivery (CI/CD) environment for almost any combination of languages and source code repositories using pipelines, as well as automating other routine development tasks. While Jenkins doesn’t eliminate the need to create scripts for individual steps, it does give you a faster and more robust way to integrate your entire chain of build, test, and deployment tools than you can easily build yourself.
Before Jenkins, the best a developer could do to avoid breaking the nightly build was to write and test their code carefully and successfully on a local machine before committing it. But that meant testing one’s changes in isolation, without everyone else’s daily commits. There was no firm guarantee that the nightly build would survive the latest commit.