What is the difference between IPSec over GRE and GRE over IPSec?

In IPSec Over GRE, GRE Tunnel should brought up first and IPSEC Negotiations will takes Place Over the GRE Tunnel. All Ipsec Traffic will be Encapsulated with GRE Header.

in GRE Over IPSec, IPSec should brought up first and Traffic Destined through the GRE Will Passes through the IPSec VPN and the traffic cab be plain text or Encripted based on VPN requirement and can have aditional Encapsulation if tunnel mode in IPSec is used.