What is an ellipsis and how do you use one correctly?

Ellipsis

An Ellipsis is three spaced periods that denote deleted text from a quotation (Hacker 270).

As a simple tell to deleted text, the ellipses is used this way: Ziggy explained his magic trick by instructing to "multiply your age in years by 365.25 . . . that is your age in days."
To show that an entire sentence was deleted: "But mom," Chris pined,"I still have an hour left. . . . I won't be late for school."
- note the use of the period before the ellipsis.
If showing hesitation or interruption an ellipsis may be used.
A line of dots is used when a line of text in poetry has been removed.

Using ellipsis to start or end a quotation is not needed.
- This rule is excused if cutting out the last quoted sentence.
Hodges warns: "Whenever you omit anything from material you quote, make sure your omission does not change the meaning of the original."
- also pointed out: when omitting a beginning sentence, there is no need for a capital letter.

Hacker, Diana. A Writer's Reference. Boston: Bedford/St. Martin's, 2003.

Glenn, Cheryl, Robert K. Miller, Suzanne S. Webb, and Loretta Gray. Hodges' Harbrace Handbook. Bostn: Thomsom/Wadsworth, 2004.