Please read the following the best explanation from one of the best engineers on Cisco TAC of Belgium Back Bone Marcin Latosiewicz:

enjoy:

Understanding ASA IPSec and IKE debugs - IKEv1 Main Mode.

https://supportforums.cisco.com/docs/DOC-14044

Understanding ASA IPSec and IKE debugs - IKEv1 Aggressive Mode.


https://supportforums.cisco.com/docs/DOC-13715