let me throw a another one here "QA Environment"
Basically, everything related to testing will happen here including Feature Testing, Exploration Testing, Build Testing, Regression testing etc..
Once we are sure about the release build, we move it to Stage.
My Team has Stage environment but we treat it as a Locked environment and is houses same configurations and code as Production Environment. We use it as copy of current released build and to compare behavior of various user stories of QA.
Test data on this environment should be also as close as actual production so that end users (clients) can have proper demos / training on this one before actually doing anything on production.
Once release build moves to this environment, Every tests must pass here, with 0 Bug count.
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