Usage varies both within English and in other languages, but the usual convention for the most common dashes in printed English text is as follows:

4.1.2.2 Subtle differences in punctuation.4.1.2.1 Simple equivalence (or near-equivalence) of paired parenthetical marks.4.1.1.2 Inversion of the function of a colon.4.1.1.1 Simple equivalence (or near-equivalence) of colon and em dash.3.1.5 Parenthetic and other uses at the sentence level.