Tie Sing Chie asks, “What’s the difference in terms of usage between the single quotation mark (‘) and the double quotation mark (“)?”
Quotation marks are used mainly to quote speech, sentences or words. Both the single and the double quotation marks serve that purpose; the difference in their usage comes from geographical preferences.
Traditionally, the double quotation mark was used in the United States while the single quotation mark was the preference inside the United Kingdom. Recently, though, some British pubblications started to adopt the American usage, which is becoming the de facto standard (see a quotation from The Guardian below).
Notice that when you use nested quotations you should invert the quotation marks, for example:
My mother said, “John told me, ‘I will not go there.'”
Quotation marks can also be used to express irony:
Uncle Joe was really “sad” about it.
The only point where there is a clear distinction between the American and the British styles is the usage of punctuation with the quotation marks. In American English commas and periods, even if not part of the quotation itself, need to be included inside the quotation marks.
Cultists are camping out in front of Apple stores; bloggers call it the “Jesus phone.” (NY Times)
In British English, on the other hand, the commas and periods will be included inside the quotation marks only if they were actually part of the quotation, otherwise they will go outside.
Margaret Jay ruefully reflected that all Blair’s considerable achievements would be “terribly undermined, and probably fatally undermined, by what I think of as the tragedy of going into Iraq”. (Guardian.co.uk)