Chapter 11 IPsec VPN for FortiOS 5.0 : IPsec VPN concepts : Phase 1 and Phase 2 settings
  
Phase 1 and Phase 2 settings
A VPN tunnel is established in two phases: Phase 1 and Phase 2. Several parameters determine how this is done. Except for IP addresses, the settings simply need to match at both VPN gateways. There are defaults that are appropriate for most cases.
FortiClient distinguishes between Phase 1 and Phase 2 only in the VPN Advanced settings and uses different terms. Phase 1 is called the IKE Policy. Phase 2 is called the IPsec Policy.