They are used for different aspects of networking.
The network mask is used to determine which subnetwork a host is on and a wild card mask is used when configuring access control lists. The network mask has a form such as 255.255.240.0 whilst a wild card mask has a form such as 0.0.0.31.
NP - I was making the point that the network mask has 255 in the leftmost octet(s) whilst a wildcard mask has 0 in the leftmost octet(s). Having said that, I suppose that a wildcard mask *could* be something like 126.96.36.199, but that's beyond the OP.
I agree that when XYZ has covered access lists, all will become clear.