Footer and Sidebar Font Size Change

Hi,
I am familiar with the highend options area of font settings, but am wondering how do i know which one of those is related to the footer area and sidebar area…meaning…there is
header 1
header 2
header 3
and so on, but how do i know which one is for which area?

can you tell me how to adjust the font size and thickness of the footer area as well as the sidebar? they are both in the widgets area, but it doesnt let me adjust the font there either.
Please advise.
Thank you in advance for your help
Blessings