It is the typical Nigerian prince scam, OP. It is about offering you money, but having to send a deposit first in order to access the fortune which they are alledging you just won, it is one of the oldest and more widespread scams of the internet. Actually, because internet was invented it was called "La estafa del galeón español" in which someone from a company in the Spanish India's was willing to give you a fortune within a Spanish warship, if you accepted to pay the fees for transportation and tariffs over the ship, which was usually docked in some coast of an hostile reign against Spain.
Anyways, whatever you do, never give attentions to those offers which are too good to be true, because they are never true and nobody is going to hand over millions of dollars to random people on the internet because of the sake of it.
Also, beware of scam webpages which disguise themselves as gambling services, when in reality they are ponzi and pyramid schemes.