This is a way to do the set indentation of a paragraph. Using style sheets lets you do some of the fancier stuff on web pages. The first line will be indented, by the number of inches or centimeters defined by the tag within the style tags. This is the other way, probably the better way, to do indentation rather than use the preformatted tag.
And you can create your own version of the blockquote tag, setting the exact size of the margins at each end rather than using the set distance of the blockquote tag.