Let's say we have a custom field called Customer. This is a select list with different values that users can select while creating an issue. If JIRA is used by multiple teams, each working on a different project, it's quite possible that the customer list will be different. One project may cater to a different set of customers than others. One approach to deal with this situation is to enter all the customers in a single list, but this will lead to confusion among the team members who raise the tickets and it will also lead to errors because users might select wrong customers.
A different custom field can be created for each project to deal with this problem (each having its own list of customers), but this leads to redundancy as we will store the same type of information.
JIRA's custom fields offer a solution to this problem using context. Perform these steps to create a new context:
Go to JIRA Administration | Issues...