Sitecore content serialization saves items such as templates, renderings and settings as files, so they can be stored in source control. Developers can then move changes between environments in a controlled way. Serialization also makes deployments repeatable, which lowers the risk of manual errors when releasing new features.
This supports a normal development process: changes are reviewed, tested and deployed together with code. It also helps new developers set up a working environment quickly.
Sitecore provides tooling for serialization, including the Sitecore CLI.
Our engineers handle this in platform implementation.