Difference between "vmkload_mod xxxxx" and "esxcfg-module xxxxx"

I have found some articles talking about essentially the same thing except the command.  One talks about using the command

vmkload_mod xxxxx

while the other one talks about using the command

esxcfg-module xxxxx

where xxxxx is the name of one module.  Both commands talk about the same module.

So, what is the difference?