Mathematics is full of identities. When we talk about the number theory, an identity is defined as something which when applied to something gives back that same thing. There are two types of identities when we talk about operations. One is additive identity and another is multiplicative identity. Multiplicative identity is the one which when multiplied to any number gives the same number. For example in case of numbers multiplicative identity is 1. For example: $5 \times 1 = 1 \times 5 = 5$. Here, we are going to discuss about additive identity in detail.