Today's software companies maintain a lot of projects and to keep development and deployment activities keep go on for each team without any friction, CICD comes into the picture.
Generally, in software development, we create two separate environments for a product: UAT and Prod. UAT is the deployment setup, which is meant for User acceptance testing and is generally used by alpha testers, developers, product managers, and internal folks of a company. On the other hand, Prod is the production environment that is used by users.