A sher is a form of poetry in Urdu, essentially a couplet. Sher is also sometimes referred as Ashaar. Although this definition is extraordinarily simple, it is essentially correct, because a sher is not bound by any rules. The only rule is that every sher must convey a complete thought by itself, without requiring any external information. A collection of sher couplets is called a ghazal. The following is an example of sher, composed by Mirza Ghalib:

nahii.n ki mujhako qayaamat kaa etiqaad nahii.n

shab-e-firaaq se roz-e-jazaa ziyaad nahii.n

It is not that I do not have faith in the day of judgement

But the night of separation is not less than the day of judgement.

What the poet is trying to say is that he trusts that the day of judgement would be very painful, as it has been described in Qur'an and Hadith; however, this night of separation from his beloved is not less painful than the day of judgement.