HD box changes normal signal into miracle

What is it specifically that the HD box does to the HD signal to enable HDTVs to have such great picture quality?

The HD box is sort of like a choirmaster. Imagine thirty 5th graders all standing together on a stage singing whatever holiday songs they want without any direction. It would sound like a busy fish market. The choirmaster (the HD box) has the ability to tune in one particular little girl’s pure voice singing a particular song from all the noise, and then filter only her voice for her mom and dad who are listening in the audience so it sounds like a beautiful solo.

Some kids have low-quality voices (standard-definition TV signals), while other talented children who have gorgeous voices should have an agent and sing on Broadway (high-definition TV signals). The HD box decodes the inbound digital signal for a particular channel and isolates it from all the rest. When the signal is decoded, there is more sound and picture available coming in from the source to display a high quality HD picture with surround sound.