At Propel, they continuously ship improvements to their service, utilizing continuous integration and delivery processes to ensure consistency and confidence in their deployment notes. They distinguish between different types of improvements, including bug fixes, feature additions, and refactors, each requiring unique consideration in prioritization, implementation, testing, review, deployment, and communication. Bug fixes aim to improve the customer experience, while feature additions introduce new features for customers to use. Refactors improve the organization and maintainability of their codebase, rarely affecting the customer experience.