After you clicked on List all extensions in the Main Menu-> Web Translation System on the left side, then picked one, clicked on its title and the list of all languages for the extension appeared, you may view various definitions near the language acronym:

       a) in progress
            It's set by the first translator who registers him/herself as
            official translator of an extension

       b) testing/QA
            It's set by the first official translator once his/her localization is
            complete but at the same time there is the necessity to check
            completeness/correctness before changing the status in
            "Released", and the translator has to set this status in order
            to change the status in "Released"

       c) Released
            It's set by the first official translator after his/her complete
            localization has been checked and it's complete/correct

 
Note: once the status has been set in "testing/QA" it's impossible to set it back to "in progress", and once the status has been set in "Released" it's impossible to set it back to "testing/QA".
When the first official translator sets the status of his/her localization in "Released", the developer gets a notification email.

You have to be logged in order to access to the Web Translation System.