A single character, not . . . (period space period space period).
Indicates missing text.
Preceded and followed by a single space: x … y
At the end of a sentence, or when used in conjunction with a comma, question mark or exclamation mark, the preceding space is dropped.
x…. Y (end of sentence, 4 dots total)
Rarely used: x,… y or x…, y
Windows: alt+0133 on the numberpad.
Part of a series on punctuation.