The notation Z_n represents the set of integers modulo n. This means it includes the integers from 0 to n-1, where numbers wrap around after reaching n. For example, in Z_5, the elements are 0, 1, 2, 3, 4. In Z_n, addition and multiplication are performed modulo n. This means that when the result of an operation exceeds n-1, it wraps around to start from 0 again. This structure is fundamental in areas like number theory and cryptography, where modular arithmetic is widely used.