What is the difference between SD quality & HD quality?

The SD quality plan allows a bandwidth up to 4Mbps which is sufficient to watch Netflix videos on 480p resolution without buffering. The HD quality plans allow a bandwidth up to 8 Mbps which is sufficient to watch Netflix videos on 720p or 1080p resolution. Netflix provides 3 different subscriptions; Basic, Standard and Premium (https://www.netflix.com/signup/planform) The Basic subscription provides content in 480p resolution while the Standard & Premium provides content in 1080p or higher resolution. However, not all content is available in HD quality. 480p resolution is the recommended quality level on a smartphone to watch Netflix.