Poetic license is also known as artistic license or dramatic license. It is a term that is used to signify deformation or complete unawareness of information. It could even be considered as varying of a well-known work that an artist may embark on in the name of art. It also refers the poet into ignoring some of the grammatical errors for poetic effect. This effect is neither considered to be "good" nor "bad". It is basically used in order to fill gaps or in order to make a rhythmic composition.
For example, Mark Antony's "Friends, Romans, Countrymen, lend me your ears" from Shakespeare's Julius Caesar would theoretically have need of the word "and" previous to "countrymen", but this is not there and this is done in order to conserve the rhythm of iambic pentameter.
For example, Mark Antony's "Friends, Romans, Countrymen, lend me your ears" from Shakespeare's Julius Caesar would theoretically have need of the word "and" previous to "countrymen", but this is not there and this is done in order to conserve the rhythm of iambic pentameter.