One thing I would add to the above answer is that poetic license is NOT the freedom to throw out all grammar and spelling rules just because you can. One thing students often do with poetry is ignore grammar, spelling and punctuation with the excuse that "It's poetry - it doesn't have any rules." This isn't completely true.
Poetic license is the freedom to bend and twist language standards with a purpose. Usually that purpose it to avoid being too literal. Artists do it as well as poets, and often receive harsh criticism as a result.
Some of the best users of poetic license (e.e. cummings and Lewis Carroll come to mind) did not simply avoid rules because they could and certainly did not do it by accident. Poetic license is an intentional choice to deviate from a written norm - so be prepared to defend yourself and your choices.
there is nothing in this term that can confuse you..just try to think a bit.licence means freedom.poetic licence is the freedom to write.it is not something democratic that you can write anything.it is the freedom that you can write in your own style.you can twist language or forget its rules while writing poetry.you dont hav to follow the rules as you hav to follow in prose.it means departing from normal prose standard of accuracy.you can use syntax grammar or pronunciation in your own way if you want to produce certain effect in your poetry.
in short this liecence means deviation from rules to acheive desird results in poetry.for example personnification inversions are frequently used in the poetry.
simply put, poetic license is the freedom a writer takes to deviate from convetional and pre-conceived thoughts of what poetry should be. the writer does the to create a certain effect and/or to leave a certain impression or feeling with the reader