(* whatever *) is an "attribute" which is sort of like a magic comment; simulators that understand it can use it as a hint to improve performance, and those that don't should just ignore it.  The results of simulation should be the same.

desc and units are special attributes for Spice-like simulators that support Verilog-A; they tag the associated variable as operating-point information.  Spice built-in models (like BSIM3) have op-pt info such as gm, gds, etc. that you can print out or plot; these attributes give the same capability to Verilog-A modules.