postman variables in body code example

Example 1: postman environment variables in body

{ "customer_id" : "{{cust_id}}" }

Example 2: Postman Variables

just like variables in Java. 
we can create variables in postman to reuse the value 
1.Global variables: accessible everywhere in same workspace 
2.Environment variables: accessible in selected environment 
3.Collection Variables: belong to the collection itself and 
only accessible within the collection