Application VIP is basically use to manage third party web based application through clusterware. Below is a sample example of managing Apache service using clusterware:-
1) Create a application VIP resource
crs_profile -create myappvip -t application -a $ORA_CRS_HOME/bin/usrvip -o
2) Register the resource with clusterware
3) Create a cluster type resource to manage your application like ACTION_SCRIPT is required to start,stop, clean and check the application availability. Here is also mentioned the resource dependency with application VIP.
Let's say apache service get started on host01..in case if host01 goes down due to some failure in that case myapache will be failover to another node along with the application VIP.
From 11g release 2 onwards you can use appvipcfg interface to create the application VIP resource and you can also assign server pool instead of using node name.
You do not need create an application vip or resource if you are just managing database resources. Since Oracle provides full clusterware functionality, it can be used just like any other clusterware in market for managing other non db resources as well.