What does Turbo have to do with proxies?
A quote from Opera themselves, about their Opera Turbo service.
How does Opera Turbo work?
The technology behind Opera Turbo is a proxy server with server-side compression of webpages. A compression rate of up to 80% can be achieved, in part by reducing the quality of images. If you want to view an image uncompressed, right-click on the image, and select "Reload Image in Full Quality".
Clearer now ?.