Agilent does not use any particular file extension for its raw data files. As they are text file they use the standard *.txt* extension.
Information about the array design characteristics such as spot location, and about the features like id conversion is generally stored in Agilent raw data files.
In an experiment carried out using Agilent technology you will have one *.txt* file for each of the arrays or slides you hybridized. If you are doing a one-color hybridization the file will contain information just for one channel signal. If you are doing a two-color hybridization the file will contain information for two channel signals.