Tink-ing is the process of undoing your knitting stitch by stitch ("knit" backwards). It can sometimes be painful, but as is the case with my knitting, often necessary. Especially if one gets distracted easily by what's on TV, or noises from down the hallway, or pictures of kittens. Kittens!!
It can be really frustrating to work hard on a piece of knitting only to have to take it all out but it is important to stay positive and remember how awesome your hat/sweater/shawl/whatever is going to look when it is absolutely perfect and mistake-free.
My grandmother taught me to knit when I was younger but I couldn't do anything fancy. I could knit or purl but did not know how to follow patterns or make anything other than either a garter stitch or stockinette stitch scarf (these always curled up and I always thought it was because I was doing something wrong, until I recently learned that stockinette pieces have a tendency to do that!). I started knitting in earnest several months ago after taking some group classes at Stitch DC and now I LOVE to knit. However, I still have lots and lots and lots to learn, so for me, tinking has become as much a part of my life as knitting and I embrace it just as wholeheartedly.