What forms a rule?

A selector and it's properties form a CSS rule.

Selector Description Example
* Universal Select all elements *{color: green;}
Type Selects the specific element p {font-family: helvetica;}
ID Single value can only be used once #Group {color: green;}
Class Can be used multiple times in html .brand {font-weight: bold;}

Typography

Tag Description Values
font-family typeface of font 'Times New Roman', Serif
font-weight Specifies weight of font bold, normal, lighter, bolder
font-style Specify italic text normal, italic, oblique
text-transform Specify uppercase or lowercase letters in text uppercase, lowercase
letter-spacing set horizontal spacing between individual characters length values 2px or 0.5cm
word-spacing set spacing between words in a text length units 3px or 0.2em
line-height how tall you want each line to be values can be unitless 1.2 or length value 12px, 5%, 2em