When you put this in an external stylesheet:
body {
background-color:black;
}
p {
color:white;
font-size:12pt;
}
you were using two type selectors. "Selector" is the name for the thing which selects which part of the Web page to apply the styles to. So the two "types" which these styles will affect are BODY elements and P elements.
Every "type" of HTML element can have styles applied using this method. All elements of that type type will be affected by the styles. You cannot have some paragraphs which have 12pt font size and some which were 10.
Type selectors are useful for formatting all parts of a Web page (or many pages) the same way but is also very restrictive.
