An environment is one or a group of gateways of any given platform. You might have a set of synchronized gateways in your on-prem data centers and another set of synchronized gateways in your private cloud. In this case you would create two environments within the API Control Plane.
These different environments may support different functions. This difference in functionality between the environments is represented by 'Environment Capabilities'. It is important to use the correct agent version, because the functionality of an environment differs depending on the agent version. Therefore, the latest agent should always be used. An overview of the 'Environment Capabilities' can be found here.
The minimum recommended requirements for production are as follows:
512MB RAM
1 CPU
5G Disk
Stages
Stages are an element of an API’s lifecycle. During development you might run the same API in different versions in different stages. So, you might run version 1.0 in production and 1.1 in development. The API Control Plane at this time has built in support for production and non-production (aka development) stages. Every environment is assigned to a life-cycle stage. This means it is not possible to create an environment that spans two stages.