Travis CI is a continuous integration service used to build and test software projects hosted on GitHub. It automates the process of software testing, making it easier for developers to ensure their code is reliable and functions as intended. By integrating directly with repositories, Travis CI allows developers to set up tests and deployment processes seamlessly. It supports a wide range of programming languages and can be configured using a .travis.yml file to specify the testing environment and script details. With features such as parallel execution, build matrices, and deployment automation, Travis CI streamlines the development workflow.