CodePipeline

A fully managed CI/CD pipeline.

Pipeline is what encompasses all components.
Stage represents a step in the pipeline. The most common steps would be Source -> Build -> Deploy. You may add many stages, so use your creativity.
Action Groups group several Actions together.
Actions do things. The can pull source code, build and run tests, deploy to production, invoke a _Lambda, invoke a _CloudFormation template.
Artifacts are zips containing files outputted by an Action. An Artifact can be passed to any future Actions and some Actions require to input an Artifact and can optionally output an Artifact.
Stage Transitions link the pipeline stages together.