Hi LynnJ
I'm no expert but brightness controls black level which allows you to see the detail in dark scenes. Contrast is what you want to be low in order to avoid burn-in. This controls the white level and its' intensity. I'm gonna quote Mr. Bob on the issues of burn-in:
"As far as screenburn goes, NO EXTENDED-TIME FIXED IMAGES. EVER. No MSNBC, no FOX, no fixed-image/border video games, no ticker tape reports burning that band into your phosphors. You'll have your hands full, probably, just keeping the black/grey bands from being seen on your screen while bright and white images are there after awhile, due to the mixing of standardized aspect ratios in this crossover era between NTSC and HDTV.
If you absolutely have to have fixed images up there for any length of time, turn your contrast low for the duration, and save the bright images for when you're watching something really spectacular. I even keep my contrast low when I watch Jay Leno's monologue every night, turning it up for the better parts of the program. Brightness is not the bugaboo on burn-in, Contrast is. Brightness, a misnomer, controls the background darks; Contrast controls the foreground bright areas."
I hope this helps.