While they are also seen in Greece, the Balkans, and sometimes Italy or France, the Turkish toilet is most common in its home country, particularly in rural areas. It is often referred to as a hole in the ground - for that is exactly what it is, albeit a hole with pipes beneath it and a porcelain cover.

Using a Turkish toilet for the first time can be an alarming experience for Westerners. The most daunting of the problems is usually that there is nowhere to sit: one must squat to use the facilities. Cleaning up is another frequent concern, as toilet paper in public bathrooms is rough and uncomfortable if available at all.

While Americans past the potty training stage don't even think about how to use the toilet at home, they may find a few tips useful when they are expecting to encounter a Turkish toilet. There will probably be two oblong spaces marked on the porcelain, either as depressions or colored sections, which indicate where the user's feet should be placed. Women usually have a much more difficult time using these toilets; if not wearing a skirt they will want to be careful to hold their pants out of the way. A small pipe is almost always present, connected to a knob on the wall - this is provided for washing up but is much less sophisticated than a bidet. Those who choose to use this will probably find it ill-aimed, too cold, and at a much higher pressure than expected. While public toilets are generally free, the toilet paper is commonly kept outside the entrance. To get any, one must pay the attendant a small charge - usually around 350,000TL, about 35 U.S. cents. The paper given is sometimes humane and other times closer to napkins or paper towels. The state of Turkish plumbing is such that no toilet paper should be put into any toilets: a wastebasket is provided instead.

Tourists who find they are terrified of Turkish toilets, though, need not wait until they leave the country to use a bathroom. Virtually all hotels have Western-style toilets - which still have the washing nozzle and poor plumbing - in the rooms, though smaller pensions (similar to bed-and-breakfasts) may only have the Turkish style available. Western toilets are also easy to find throughout the country, though there may be only one or two in a public restroom that also offers three or four Turkish toilets. In more rural areas, Western toilets may be even harder to find, though atesh points out that they are actually more common in Turkish homes - it's just the public toilets that are still old-style. The Pamukkale Ekspresi, an express train that runs between Istanbul and Denizli. First-class sleeper cars feature porcelain Western-style toilets, but in the second-class coach car only a stainless steel Turkish toilet is available.

http://dept.kent.edu/geology/turkey/images/chr074.jpg (location unknown)
http://www.amanita.net/images/turkish-toilet.jpg (taken at Pergamum - I used the Western toilet in the next stall)

My own encounter with a Turkish toilet happened in the Cappadocia area while our tour bus was stopped at a restaurant for lunch. I excused myself from the table and found the bathroom. There were three stalls, each with full-length doors and walls - each effectively a little room - and a frosted window in the door. All were empty, so I pulled open the door of the first stall - Turkish toilet. After finding the others were the same, I took a deep breath and stepped in. It was very clean, so I carefully slipped off my shoes and tried to figure out how this was going to work. Because I knew no one would be able to see, I eventually decided to just take off my pants - a procedure I definitely recommend for women (though Chattering Magpie suggests that if you leave your pants on, take everything out of the back pockets!). After stepping back into my shoes, the process was much easier.