What does Kilen Dryed mean?

Its kiln dryed. It basically means the wood is dried in a oven. It makes the wood cheaper to transport also more stable. Basically there getting the moisture content reduced in the wood. It will also make it stain or finish better.

It's purpose is to provide a wood where the moisture content is reduced enough to eliminate most of the shrinking and twisting. A 2X4 is actual 2" X 4" then it is kiln dried and shrinks. Some woods need more time to dry to even further lower the moisture content. This takes more money. Woods like hardwood flooring fall into this category. And you can buy cheaper wood from sources like Lumber Liquidators which have higher moisture content and thus a little bit cheaper. Down side is when you install it, the floor buckles.

Like they said, and if you want more: http://en.wikipedia.org/wiki/Wood_drying Be safe, GBAR

Thank you all, brothers. It is very useful to me.
Have a good day.

As stated, KD (kild dried) lumber has had is moisture content reduced in a very controlled fashion. It is done with heat, humidity, and quite a bit of science. Done incorrectly you can cause the wood to bend, twist, check, cup, and lose its color.

Nearly all hardwood flooring and lumber for woodworking must be kiln dried, or air-dried over many many months. Your climate and humidity level in vietnam is not conducive to air-drying lumber to acceptable levels I imagne. Most hardwoods are dried to between 6-12% moisture content for use in woodworking and millwork.

Technically, kiln-drying is achieved at 19%, but that's still too wet for interior millwork and furniture applications in my opinion.

If you're an exporter, you probably have dealt with HT (heat treated) lumber as well. HT is often required to kill organisms in the wood before it is shipped to other parts of the world. It is not the same as kiln drying.