Difference between snat and wildcard ?

I'm going to guess that you mean NAT. But in any case, fundamentally different things.

1. A wildcard VIP, by default does not translate the destination address (though it can), and of course it can load balance.

    

2. A SNAT translates the source address, does not in and of itself load balance, and you cannot target a SNAT the way you can a VIP or NAT.

    

A regular VIP would translate the destination address, and only translate the source if a SNAT was applied to it.