Z_5 is a mathematical notation that represents the set of integers modulo 5. This means it includes the numbers 0, 1, 2, 3, 4. In this system, numbers wrap around after reaching 5, so for example, 5 is equivalent to 0, 6 is equivalent to 1, and so on. In Z_5, addition and multiplication are performed modulo 5. For instance, adding 3 and 4 results in 2 because 3 + 4 = 7 and 7 mod 5 = 2. This structure is important in various areas of mathematics, including number theory and abstract algebra.