MCO LAX 16/0800 0956 UA 273 F8 Y9 B9 M9 H9 Q9 V9 W9 S9 320
Basically, flight leaving from MCO to LAX leaving 0800 arrivning 0956 on UA fllight 276. Then its a listing of the differnet fare classes and how many seats are available. The maximum it will show is 9 so if there are 432423 seats it will still show only 9. and the last item indicates aircraft type (in this case an airbus 320). Then it continues into its connecting flights
To check fare classes for united, you can try this thread
http://www.flyertalk.com/forum/showthread.php?t=113792
Award availability is only available for certain airlines. (united doesn't show)
I don't know about other airlines.