Hyphens are used for different reasons than dashes. The following paragraphs explain the distinctions.
Use a hyphen
NOTE: Most prefixes are no longer hyphenated. A usage table for common prefixes is in The Chicago Manual of Style.
Do not use a hyphen
There are two basic types of dash: an em dash (—) and an en dash (–). When using dashes, keep in mind
Dashes are not surrounded by spaces.
The first word after a dash within a sentence is not capitalized unless it is a proper noun.
Use an em dash to
Set off an explanatory or appositive series
The company has established a worldwide customer base in all major markets—the U.S., Europe, Japan, Korea, and Taiwan.
Set off parenthetical elements more sharply and emphatically
The 1990 plan—both the planning process and the finished product-attests to the increasing level of maturity and effectiveness at SEMATECH.
Set off a phrase that typically requires commas, but one in which using commas would cause confusion
Knowledge from the SEMATECH member companies, America's equipment and material suppliers (SEMI/SEMATECH), and the Department of Defense (DOD) are brought into SEMATECH—along with information from American universities, research institutions, government laboratories and agencies, and the Semiconductor Research Corporation (SRC).
Use an en dash to indicate a range.