The tag is the tag itself, for example [ClickHere3], the text is the text used to replace the tag, for example 'Click Here' and the URL is the page to display. This approach lets you have multiple tags for the same text. However in the menu we decided to display the URL to avoid confusion.
If you search for this feature in this forum you will see how many requests we get from users, how we modified the original design that hasn't that extra 'value' field and when it was added. In the example above, old version of MaxBulk Mailer with no 'value' field made impossible to have tags with the same text since the tag itself was the text!