We use quotation marks with direct quotes, with titles of certain works, to imply alternate meanings, and to write words as words. Block quotations are not set off with quotation marks. The quoted text is capitalized if you're quoting a complete sentence and not capitalized if you're quoting a fragment.
are quotation marks that writers place around a word or phrase to signal that they are using it in an ironic, referential, or otherwise non-standard sense