pgStatTuple

Hi all, I am using v. 8.0.1, using a Windows 2003 server platform.

I want to use pgStatTuple to analyze performance problems when visiting user
sites; it is a good tool. I know how to set it up; but I couldn't find an
interpretation of what it generates as a result, so I can be sure of
interpreting its output correctly and fully. The output is:

table_len(integer) in what size unit? pages?
tuple_count(integer) how many t
tuple_len(integer) length of average tuple size?
tuple_percent (float) ??
dead_tuple_count(integer) tuples that contain dead rcds that could be
freed
dead_tuple_len (integer) how much space (in bytes?) is dead
dead_tuple_percent (float) % of dead space vs entire space for object
free_space (integer) how much space (in bytes?) is already allocated
and free
free_percent (integer) % of free space vs entire space for object

Can anyone help? May also require definition of 'tuple' when used in a
PostgreSQL sense, also. Thanks for any help you can give.