What is the difference between a Policy-based VPN and a Route-based VPN?
https://kb.juniper.net/InfoCenter/index?page=content&id=KB10105
A Policy Based VPN is a configuration in which a specific VPN tunnel is referenced in a policy whose action is set as Tunnel. ( security policies )
A Route Based VPN is a configuration, in which the policy does not reference a specific VPN tunnel. Instead, a VPN tunnel is indirectly referenced by a route that points to a specific tunnel interface.
The tunnel interface may be bound to a VPN tunnel or to a tunnel zone