Continuous integration is abbreviated as CI. It is a DevOps process allowing developers to integrate new code with automated built and run unit tests. Different tools and platforms can help in the same. CI is the automation of the integration of codes. A no. of sources integrate to particular software. The reaction starts with source code which gives the output via build.
The output is saved for future access. It is used for CD. When a developer commits a code, the automated tools give the output. The build must be quick. This will help to identify problems (if any) with integration quickly.
The CI and continuous delivery are an integral part of the system called the CI/CD pipeline. You must check out my brief illustration in a 1- minute video to know CD (continuous delivery). The code thus built undergoes unit tests. This is to ensure that the code performed is running as expected by the developer.