Resource Usage explained

Load Time: The time from when the debug widget was instantiated to when the last view was rendered (not including debug widget views)

Elapsed Time: The time from when the php process started in the request, to when the last view was rendered (not including debug widget views)

Mem: Returns the amount of memory, in bytes, that's currently being allocated to your PHP script

Mem Peak: Returns the peak of memory, in bytes, that's been allocated to your PHP script (over the life of the script I believe).

Session Size: An estimate of the $_SESSION variable in KB. Here is the exact method used:

printf('%0.3F KB' ,mb_strlen(serialize($_SESSION))/1024);

by jymboche: http://forum.phalconphp.com/discussion/1532/introducing-phalcondebugwidget-pdw-