[ame="http://en.wikipedia.org/wiki/Ellipsis"]Ellipsis[/ame] (plural ellipses; from the Greek: ἔλλειψις, élleipsis, "omission") is a mark or series of marks that usually indicate an intentional omission of a word or a phrase from the original text. An ellipsis can also be used to indicate a pause in speech, an unfinished thought, or, at the end of a sentence, a trailing off into silence (aposiopesis) (apostrophe and elipsis mixed). The ellipsis calls for a slight pause in speech.
The most common form of an ellipsis is a row of three periods or full stops (...) or pre-composed triple-dot glyph (…). The usage of the em dash (—) can overlap the usage of ellipsis.
The triple-dot punctuation mark is also called a suspension point, points of ellipsis, periods of ellipsis, or colloquially, dot-dot-dot.
I don't generally think about it before using it.
When I'm typing and actually take a pause or have another related thought,... <--- I indicate it like that.