Either a test bed could have many test environments in it, or a test environment could have many test beds.
A testbed is a platform for experimentation for large development projects. Testbeds allow for rigorous, transparent and replicable testing of scientific theories, computational tools, and other new technologies.
The term is used across many disciplines to describe a development environment that is shielded from the hazards of testing in a live or production environment.
In software, the hardware and software requirements are known as the testbed. This is also known as the test environment.
Testbeds are also pages on the internet where the public is given the opportunity to test CSS or HTML they have created and are wanting to see the outcome.