It is required if you are doing color or patterned backgrounds but is otherwise optional. H1 is the largest, H5 is the smallest. Automatically makes a blank line above and below. Puts the lines of text into a paragraph. Does not indent.
Web browsers ignore spaces and tabs.
Bold, italicize, or blink the text. Remember, blinking gets old fast. It restarts the text at the left margin. This can be used within other tags. This has no bullets or numbers.