When modifying the Normal Style and the Heading 1 style, which font should I specify.

I want to use Arial 12 font.

For the Normal style, do I use the regular Arial font or select the Arial Body font?

Also for Heading 1, do I use the regular Arial font or select the Arial Heading?

It's so confusing to know which one I should use.

Your help is appreciated.

Thanks in advance.