Fastlane is a scripting tool to simplify the CI pipeline. It contains commands to build iOS and Android projects, but also contains many other helpful tools to help with building a custom pipeline.

You can create your own actions, and is not limited to just native projects, but can also be used for other platforms, either by adding 3rd party plugins or creating your own commands.

One of the actions most widely used, is the "match" command, to simplify the painful process of adding and maintaining iOS signing certificates and provisioning profiles.

Why do we adopt this technology?

There are many alternatives to use. You can use custom scripts, or use plugins from your CI solution.

However, Fastlane is already used for handling iOS signing certificates, and has yet to find a worthy competitor for handling this. By using Fastlane for the other actions, you limit the amount of tools used in the same pipeline. You can also rely on the available community plugins in Fastlane, or make custom plugins. Using a scripting tool and not relying on specific CI plugins, limits the dependency of that CI system on your pipeline.