The ampersand (&) is a ligature of et, Latin for and. In formal English, its main use is in titles, such as "Simon & Schuster." It should never be used in prose as a replacement for "and," however common this practice may be in Internet communications.

On occasion, the ampersand is used in place of "et" in "et cetera" (Latin for "and other things") or "etc.," abbreviating to "& cetera" or "&c."

In HTML the ampersand is a reserved character for specifying extended characters, like é (é), therefore a literal ampersand is specified with the & sequence.

For a good historical analysis of the ampersand, read Adobe's The Ampersand.