What zakat is
Zakat means purification and growth. It is an act of worship and a duty, not only a kind gift. Allah mentions it together with prayer in many verses, for example Quran 2:43.
Prophet Muhammad ﷺ taught that Islam is built on five pillars, and zakat is one of them. When he sent Mu'adh to Yemen, he told him to teach the people that Allah has made zakat obligatory on their wealth, taken from their rich and given back to their poor. Quran 51:19 describes the share of the beggar and the deprived as a right in the wealth of the righteous, so it is not a favour.
Zakat cleans the wealth of the giver and the heart from greed. It also supports people in need.