If you send the same message with a happy smiley face symbol : ) the person would take that to mean you were smiling when you sent the message and know you were joking with them. In a face-to-face communication you would laugh or really smile to convey the "I'm joking around or kidding with you" emotion.
Beside this, what does this symbol mean?
something used for or regarded as representing something else; a material object representing something, often something immaterial; emblem, token, or sign. a letter, figure, or other character or mark or a combination of letters or the like used to designate something: the algebraic symbol x; the chemical symbol Au.
What does the double S symbol stand for?
Wikipedia says: "The section sign (§, Unicode U+00A7, HTML entity § ), also called the "double S", "sectional symbol" or signum sectiōnis, is a typographical character used mainly to refer to a particular section of a document, such as a legal code.