To ensure that software is reliable and robust, it is important to consider using multiple environments in the process of software development. The environment setup I am most familiar with is one that has a development, staging, and production environment, sometimes referred to in their condensed form: Dev Env, Staging Env, and Prod Env.
The development environment would be the first stage where a developer could deploy and test their code. It's like a sketchbook with existing sketches, where you can draw your first drafts of an illustration. This would be the first stage where potential bugs are found and fixed before moving onto the next environment: staging.
The staging environment is the next stage where code is deployed for additional testing. This is also the stage where Quality Assurance testing is performed. Staging is the environment where developers can test interactions between dependencies and is meant to mimic a production environment. Staging is where a variety of test cases are performed which either reveal bugs or affirm that the code is operating as intended. Once the code and all the test cases are verified, the code is deployed to the final stage: production.
The production environment is the stage where code is live to users and fully functioning. Although, that doesn't mean there aren't bugs. 🐛😉