I need "general information" about nude  sleeping.

Probably favoured by those who ask a lot of 2 dollars questions. i.e.
too cheap to buy a pair of Pyjamus!
Mongolia

Is it a form of art or entertainment or both?

Nelson, there are some very attractive paintings and sculptures that
present it as art  - which I find very entertaining.

And  - Shoaib, you'll like this -  there are definitely no upfront
costs (pajamas or whatever) and no constrictive or binding conditions.
 I am not sure how to include 100% payout, but it sounds like what you
have been looking for.  ;-)

Shoaib,

why anyone would wear pajamas to bed when Nude sleeping is the best.
Let me give you three reasons.
1. If you are nude, then when you move, the sheets rub against your
skin. Sometimes, for one reason or another, you fel more comfortable
and sleep deeper, if you do not have that friction on your sken.
Pajamas remove that friction.

2. Sometimes the temperature is not controlable. Pajamas give a very
efficient insulation factor. We teach Boy Scouts to always bring good
pajamas on an overnight campout because it is much more efficient than
getting a bigger sleeping bag, because the cloth is closer to the body
and traps the heat better.

3. In certain social situations. I have been to business conventions
where I shared a room with another person, and having pajamas was
expected.

This is not to imply that I like to sleep nude. Like yourself, many
learned to prefer it over pajamas. But when u have visitors in the
house, for example, wear pajamas. So give most, but not all, of your
pajamas to charity. I commend you on your decision to sleep nude.

You might want to visit this page
http://www.nudist-resorts.org/

Enjoy Nudity!!