The empty string is a syntactically valid representation of [[0 (number)|zero]] in [[positional notation]] (in any base), which does not contain [[leading zero]]s. Since the empty string does not have a standard visual representation outside of formal language theory, the number zero is traditionally represented by a single [[decimal digit]] '''0''' instead.
Zero-filled memory area, interpreted as a [[null-terminated string]], is an empty string.
Empty lines of text show the empty string. This can occur from two consecutive [[End of line|EOLs]], as often occur in [[text file]]s, and this is sometimes used in [[text processing]] to separate [[paragraph]]s, e.g. in [[MediaWiki]].