What is the board of diploma?

There's no single, universally recognized "Board of Diploma." The term "board of diploma" is vague and needs more context. It refers to the governing body *of a specific diploma program or institution*.

To understand what a "board of diploma" refers to in a particular case, you need more information, such as:

* The name of the institution or program: Is it a specific college, vocational school, or professional organization offering a diploma? Knowing the name will help identify their governing body.

* The country or region: Diploma awarding bodies vary by location.

* The field of study: A "Board of Diploma" in nursing would be very different from one in culinary arts.

Once you provide more context, I might be able to give you a more precise answer.