I bought an IdeaPad Y580. I would like to know which graphic card is running on it, and how I can switch to an option which uses less power.
To find out what graphic card is running on your system, go to My Computer and click on Properties.
You can also use an app such as Speccy, which lists out in detail the programs you have in your system.
With regard to graphic card switching, this process is automatic. To save energy / manage graphic usage, you could use switch to Balanced or Super / Power Saver mode under Lenovo Energy Management.
Alternatively, you could go to the NVIDIA Control Panel >> Manage 3D Settings, where you can then toggle your preferred graphics processor.