Why is Eid-ul-Fitr important for Muslims?

There is a simple answer to this question which lies in the fact that Muslims have just come out of fasting, which for a healthy adult male requires them to abstain from all food, drink, sexual activity, and certain other activities from dawn until sunset.

"eat and drink until the white thread of dawn appears to you distinct from its black thread; then complete your fast till the night appears;" (Sura 2:187)

The Qur'an has strict rules about when the fast begins and ends but it is also compassionate in that it allows some people who are sick, ill, menstruating, pregnant or nursing to delay their fast. It also allows children to be exempt but recommends that they practise the art of fasting by extending the amount of time they can go without food.

Being released from the burden of the fast is a very good reason to celebrate.