There are three kinds of packages one can build in the Salesforce platform, Out of which Salesforce Unlock Package is very powerful for the use-case of project deployment, release management, and CICD.
- Manage Package: Metadata is IP Protected, distributed via AppExchange
- Unmanage Package : Metadata is not IP Protected, you can protect via password but not a good way of working
- Unlock Package: Metadata elements are not locked, use it for modular development
Salesforce Unlock package provides a great way for modular development and release, Best suited for Multi org rollout of core functionalities. The below diagram illustrates the unlock packaging and release via Salesforce CLI. Core reviews can also be automated using Salesforce CLI Scanner plug-in using PMD v6.38.0, ESlint v6.8.0, and RetireJS v2.2.5. My blog on Salesforce Code Review Process has more details on that https://twirltech.in/2021/10/salesforce-code-review-process/
It’s Source driven development and deployment mechanism, comes with Platform, no-cost, fully integrated with developer IDE VS Code
Refer to the Salesforce developer guide to get your hand dirty https://developer.salesforce.com/docs/atlas.en-us.sfdx_dev.meta/sfdx_dev/sfdx_dev_unlocked_pkg_intro.htm