Congestion-control Cisco Nexus clarity

Hi, after reading about PFC on Cisco's site I've understood about 99% of it now as well as all the commands too. Two commands i'm not completely sure what they do are:

congestion-control tail-drop

congestion-control random-detect

I think they mean what the behaviour will be for each class/CoS if there is congestion, so tail-drop will just knock packets off the end of the "tail" of the buffer queue or not allow them to join the buffer is another way of saying it i suppose.

Random-detect will use the WRED settings that are put into your queuing classes, so:

policy-map type queuing bandwidth_wred

class type queuing 1p3q4t-out-q2

bandwidth percent 50

random-detect cos-based

random-detect cos 5 minimum-threshold percent 10 maximum-threshold
percent 30

random-detect cos 6 minimum-threshold percent 40 maximum-threshold
percent 60

The following random-detect settings above in the class-map are applied when there is congestion on the links.

Would you be able to clarify if you know the answer?

Cheers