XOR:
It is also called exclusive OR gate. It is an odd function. In general, it is equal to 1 if input variables have odd number of 1’s. For 2 variable it is defined as z=x’y+xy’. We don’t have muti input XOR gates because it is quiet uneconomical from hardware point of view. It is represented by 
which is actually a plus sign enclosed in a circle.
X-NOR: It is also called exclusive NOR gate or equivalence gate. It is an even function. In general, it is equal to 1 if input variables have even number of 0’s (don’t take it as even number of 1’s) . For 2 variables it is defined as z= xy+x’y’. It is represented by 
which is actually a dot (.) enclosed in a circle.
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