In the story " the twelfth night by shakespeare" ,what is it all about?

In the twelfth night, orsino attempts to win the affections of countess olivia.  a shipwrecked girl named viola disguises herself as a man named cesario and begins working for the duke.  olivia, thinking viola is a man, falls in love with him.  olivia's servant, maria, forges olivia's handwriting in letters to a steward named malvolio. malvolio thinks olivia is in love with him.  the duke asks cesario to draw olivia to him, but olivia confesses her feelings for cesario.  olivia mistakes cesario's/viola's twin brother (sebastian) for cesario, and marries him. eventually, viola reveals her identity and becomes engaged to the duke, and sir toby marries maria.so, basically, it's a huge love triangle.