With Continuous Integration (CI), developers submit small, frequent changes instead of large, infrequent changes. When another developer accepts the changes, automated tests and build steps run to ensure that the code works as expected. This action is completed frequently, many times a day with automation running each time thus insuring the code base can Continuously Integrate.
The tests and build steps are typically run in an automation server such as Jenkins or Travis. There are also cloud native/kubernetes solutions such as Tekton.
Check out these great links which can help you dive a little deeper into running the Continuous Integration practice with your team, customers or stakeholders.