Please share the exact difference between subnet mask and wildcard mask? And why we using wildcard mask in routers?

Subnet mask tells the number of network bits and number of host bits in an IP.

Number of ON bits = number of network bits

Number of OFF bits= number of host bits

Wild Card mask is used to match the IP address So that any action can be performed on them

like to drop those matched IPs.

Number of OFF bits =  number of bits to be matched

Number of ON bits = number of bits can be wild (any)

Subnet:- 192.168.10.0

Subnet mask :- 255.255.255.0

Wild Card mask :- 0.0.0.255

Subnet mask tells that 192.168.10.0 is the network

Wild card tells that all the ips which will have 192.168.10 will be matched.

Both are used to match network bits and host bits in a different way.

For Example for 24 network bits subnet mask will be 255.255.255.0  and WM will be 0.0.0.255