what is difference between single inverted and double inverted in programming languages

1[...] In common usage, there may be a distinction between the
2single and double quotation marks in this context; often, single
3quotation marks are used to embrace single characters, while 
4double quotation marks enclose whole words or phrases[.]
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7Simply: according to the charcter check for string and char
81. if char , then use '';
92. if string , then use "";