Zakat is a portion of ones wealth, that is fixed by Allah Almight. This portion is for the poor Muslim. poor must not be Hashmi or any slave who is free from a Hashmi

Zakat is an obligation

Who so ever not pay the Zakat is Non Muslim and he is worthy to be put to death Who will delay in paying its part of Zakat he is  Sinner One more important issue writing here is It will not be considered as Zakat, that any one have given meal to some poor to eat, and that meal is considered as zakat.

But if that person gives him meal and allow him to take that meal along with him, either that poor eats that or he take it away for his family, then it will considered as Zakat.

If any one give his/her home to some poor to live for some time, and considers that he have Given the Zakat, For this he must not consider this.

untill or unless he dont give a part of its wealth to the poor, obligation of Zakat is not fulfilled.

Bahar e Shariat P. No 874 Book 1 part 5