Definition:

It's not a hyphen, but a dash is a short line that serves as a punctuation mark and often represented by one or more hyphens.

The Short Dash

A little longer than a hyphen, the en dash is roughly equivalent to one half of the em (the en) — which in turn is the point size of the typeface. That is, for a 14 point font the en dash is around 7 points wide. En dashes (–) are primarily for showing duration or range as in 9:00–5:00 or 112–600 or March 15–31.

Informally, a hyphen often stands in for a proper en dash. Spoken, it's the word to, that is 9:00-5:00 is 9 to 5.

The Long Dash

Frequently seen written as a pair of hyphens, the em dash is a little longer than an en dash and is approximately the size of an em, the point size of the font. In a 14 point font, the em dash is about 14 points wide. Actual size can vary by typeface depending on the designer. Similar to a parenthetical phrase (like this) the em dash sets apart clauses in a sentence or may be used to provide separation for emphasis. Spoken aloud the em dash is simply a pause, much like a comma.
Also Known As: en dash | em dash

Examples: The hyphen and en dash are separators that connect similar bits of information such as compound words and telephone numbers (hyphens) or date and time ranges (en dashes). The em dash is a stronger version of the parentheses and commas — separating and emphasizing.