Sting Concatenation is achieved using "+" symbol which would concatenate different string
String1 = "Learing JS is Fun";
String2 = "I will continue learning";
String3 = "Goodbye";
StringMsg = String1 + String2 + String3
Sometimes there would be only one long string and to split the string into multiple lines "\" is used.
Please note that in this case the string is one , but for the sake of readability it is split to multiple lines.
StringComplete = "This is very long string spanning across multiple lines \
I am using the special key for this purpose \
Continue with more details"