Double quotation marks are used to indicate a dialogue or a quote.
e.g. He told me to "go fly kite !" or it can be used to indicate an ironic or special usage
e.g. He called himself a "Photographer" simply because he owns the latest and greatest.or for titles
e.g. Does the library have "The tales of two cities" by Charles Dickens ?Single quotation marks are used for cases of quotes-within-quotes
e.g. I asked the librarian and he told me "I will contact you should we get hold of a copy of 'The tales of two cities' by Charles Dickens".Hope this helps