Calculates the response time according to the first public comment 

Response Time custom fields calculates the 'response' or 'no response' time.

Response Time field calculates the time passed till the first public comment, where No Response Time field calculates 'no response time' and displays data for issues which still do not have any respond yet.

To define Response Time custom fields, simply

Below is a sample snapshot of Response Time custom field.

Below is a sample snapshot of No Response Time custom field. 

Searching against these fields is simple. Use the custom fields in JQL as below 

You can configure response custom fields by simply clicking on Configure context link in cog icon

Then click on Edit Response time configuration link 

You can easily configure (calendar, issue main and navigator view time formatter) the custom field according to the context