Intertextuality refers to the shaping of a text's meaning by another text through references like allusion, quotation, translation and pastiche. These intertextual references add layers of depth and influence readers based on their prior knowledge. Intertextuality can be intentional or unintentional, and comes in three types - obligatory references significantly impact understanding, optional references provide context but are not essential, and accidental references are made by readers without writer intent. Writers use intertextuality as a literary device to engage readers and demonstrate interrelationships between works.