Kiln-dried wood is wood that is sawn, placed in a kiln and dried using warm air currents. Kiln drying is a considerably faster process to traditional air drying. This method produces a much harder product usually reserved for the building trade.
Kiln Dried wood is the industry standard for construction. It is the most consistent and stable product offered after the drying process.
Smaller woodworking projects, such is with chisels or on the lathe may want to consider using air-dried wood as kiln-dried wood can be unforgiving and hard on tools.