Understanding sandbox architectures
You can use different sandbox types for different release stages. There is no mandatory configuration setup. You can use a Full type sandbox to execute your development phase, although it makes no sense at all (really high license pricing being one of the main reasons).
Let's picture an example of how you can design the environment strategy within your project's release strategy.
Consider the following sandbox architecture, which can be applied to most projects:
In this figure, Production is the only org that is not a sandbox.
We can start with two sandboxes, Dev1 and Dev2, which can be of the Developer type, and are assigned to two different developers/administrators or for two different implementations that may be unrelated.
Once developers have completed their job (meaning that the implementation is stable), the changes can be brought to the Integration sandbox...