The methods relating to sorting in the auction house can operate on many columns, this identifier is used to indicate which column is being referenced. Valid values are:

Values Edit

"quality" 

Item quality (All types)

"level" 

Item level (Only "list", "bidder")

"duration" 

Auction duration (All types)

"buyout" 

Current buyout price? (Only "bidder")

"status" 

Status (High bidder or not??) (All types)

"bid" 

Current bid (All types)

Notes Edit

Not all of these sorts are valid for all auction types, those which are seen in the WoW UI code are indicated.