Carol,
this link explains its and has pictures.
http://www.oralcancerfoundation.org/dental/tube_feeding.htm

The idea may be creepy but it is not a big deal. I had one and although I did not used it a lot it can be a life saver! Not only can you be fed you also can administer liquids and avoid dehydration.
Even if you have it it does not mean that you have to use it. You can drink and eat normally even when you have a PEG. BUT if and when the time comes that you cannot eat and drink because your mouth hurts from radiation or other issues it will save your life. It just gives you more options and a peace of mind. Many RO require that you have one. Installation takes maybe 2-3hrs, including waking up. I my case I was working in the afternoon. Removal is a snap (literally).