Blue green deployment is a way of making sure the changes you make to a website or computer program are working correctly. When you make changes, you create two versions: a blue version and a green version. You can test the blue version first to make sure it works correctly and if it does, you can switch it to the green version. This way, if something goes wrong with the new version, you can switch back to the old version quickly and easily. Blue green deployment is used to make sure your website or program continues to work properly.