About BG_USER_HR_01 field in Bug Table

Hi,

I have run a query to pull the Field Name and Field Label.

In the list of fields I can see BG_USER_HR_01 to BG_USER_HR_06, but when I go back to customization and project entities I couldn't find the same.

Some one can help and explain them, and also please help to clarify as mentioned below

Where we can check them?

Is the fields are system fields?

Can we use them?

Thanks in Advance,

Subbarao