In television terms, "HD" stands for "High Definition." High-definition television is of a vastly higher resolution than standard-definition television. As a result, the HD picture looks far clearer, sharper and more natural than SD can ever hope to deliver. If you have an older TV or have just purchased a new TV and want to know if it is capable of displaying true high-definition content, all you need to do is know where to look.
Locate the instruction manual that came with your television.
Look in the "Table of Contents" (normally one of the first two or so pages) for the "Technical Specifications." Flip to that page in the instruction manual.
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Look at the listing for "Resolution." If the resolution of the television in question is listed as 480i or 480p, you have a standard-definition television set. You will not be able to use devices like Blu-Ray players or high-definition cable boxes. If the resolution is listed as 720p, 1080i or 1080p, then you have a high-definition-compatible television set.