Differnce between unrollsrf command and smash command

Hi everyone.
What is the differnce between unrollsrf command and smash command.

now i am using smash command to create a base surface for flowing ornoments on different objects. I saw on the forum that many use the unrollsrf command and i dont understand what is the difference.

Thanks.

UnrollSrf is for surfaces curved in one direction, i.e. developable. Smash will flatten a surface that has curvature in two directions but this implies some expansion or contraction in areas so it’s not as exact. Here’s some further info on the help pages for these commands.
http://docs.mcneel.com/rhino/5/help/en-us/commands/unrollsrf.htm
http://docs.mcneel.com/rhino/5/help/en-us/commands/smash.htm

thanks for the explation