I meet every six months with both my supervisors and the third academic advisor from a related field within the same university. They form the 'panel' which then read a lengthy report (c8,000 -10,000) I give them about my research to date and then they provide feedback, criticism, avenues for research and then fill in university documentation about whether my progress has been satisfactory etc.
I find them scary, and my last one was dire - but this one has left my happy and motivated!