Well,I had no clue about kefir either until I read the thread "Probiotics for you and your chickens". That's been a couple of months ago and now the thread is many more pages.
It is my understanding that it is a cousin to yogurt but with way more probiotics.IMHO to have to tend it almost daily (when you make your own) is extra time I don't have now.
I did find one ready made here at the grocery store. It is not cheap but when I consider that it is already sweetened with real sugar and fruit plus the fact I would have to buy my milk...then it is a great buy for me.
I buy Lifeway's brand.They have good info on their site and I signed up for monthly coupons.
The first time I started it I had just started an antibiotic. I drank the kefir daily and was happy that I also didn't get the ''extra infection" women tend to get while on antibiotics.