SQL & PL/SQL

Dear All,

I am having difficulty in understanding the method in which a string is concatenated with another string in plsql. I have gone through many websites for eg. http://www.techonthenet.com/oracle/questions/quotes.php , http://www.orafaq.com/faq/how_does_one_escape_special_characters_when_writing_sql_queries
but still unable to get why do we put 3 singles quotes if we want 1 single quote at the beginning and 2 single quotes for 1 single quote if we want the single quote within a string. I know there is a logic of escape characters but its not explained properly anywhere. Could someone please explain this to me with an example since we need to concatenate very long strings.

Thanks in advance.