While Jira's built-in fields are quite comprehensive for basic general uses, most organizations soon find they have special requirements that cannot be addressed simply with the system fields available. To help you tailor Jira to your organization's requirements, Jira lets you create and add your own fields to the system, called custom fields.
Every custom field belongs to a custom type, which dictates its behavior, appearance, and functionality. Therefore, when you add a custom field to Jira, you really add another instance of a custom field type.
Jira comes with over 20 custom field types that you can use straight out-of-the-box. Many custom field types are identical to the built-in fields, such as date picker, which is like the due date field. They provide you with simplicity and flexibility that are not available with their built-in counterparts...