A QAM tuner is a device that allows one access to the newer digital cable programming.
IT IS NOT THE SAME AS THE DIGITAL TUNERS FOR RECEIVING DIGITAL BROADCASTS OVER THE AIR! (ATSC)

Starting in mid-August, the Cable system will be run entirely with this standard, meaning that viewers without these new tuners will only recieve static, blue screens, or the similarly non-entertaining or informative content!

Some channels will be "encrypted", meaning you have to have a QAM tuner specifically blessed by Charter Communications for their access (think HBO, etc.)

Where do you get a QAM tuner?
Some newer Televisions have these built in.
You'll have to investigate with the manufacturer (probably through their website) to find out if it has the QAM tuning ability.

Some DVD Recorders and DVRs have these built in, too.
The LG DR787T, the Toshiba D-VR660, Samsung DVD-AR650, Toshiba DR560/R560, JVC DRMV100B, and Sony RDR-GXD455 are just a few.
Notice that many different brands are represented in this list.

Some DVRs (Digital Video Recorders) also have QAM tuners - those made by Sony, Motorolla, and others usually feature both QAM (Cable) and ATSC (Airwave) tuners.

You can buy a stand alone QAM tuner
Ones found online can often tune into the digital airwaves, too, as well as do HDTV. Use the words "reciever box" in your search.

You can rent a stand alone QAM tuner from Charter
Charter will provide these to customers free of charge for six months. But after this six month window, these customers will have to pay some monthly fee.

We're sorry we don't know more, but we've been left in the dark along with all of you.