The occasion is Eid ul-Fitr which means 'festivity of breaking the fast'...
It is the celebration after the fast of the month of Ramadan... Ramadan is the month of the Quranic revelation, Muslims use this month to reconnect to the Quran and build a stronger relationship with Allah. This is achieved by fasting from food and s-exual activities with one's spouse during the daylight hours, refraining from foul and shameless language and actions, increased acts of charity to the less fortunate, reciting the word of God Etc...
We learn self restraint against our permitted human desires and hopefully would build stronger restraint against desires that are not permissible.
Basically making a stronger effort to be the best you can be and come out a better human being at the end... It is like a training course for the muslim... At the end of the course, we get our certificate and a feast.... We repeat the training course once every year