The difference between zakaah on wealth and zakaat al-fitr

Yes, the zakaah that is one of the five pillars of Islam is
something other than the zakaah that must be paid at the end of Ramadaan
(zakaat al-fitr). 

The former is zakaah on wealth which is only obligatory on
certain kinds of wealth, viz.: 

1-    
An’aam livestock (camels,
cattle and sheep)

2-    
Gold and silver and, nowadays,
paper currency

3-    
Trade goods

4-    
What is produced by the earth,
which includes two things:

a.     
Crops and fruits. The scholars
are unanimously agreed that it is obligatory to pay zakaah on four kinds:
wheat, barley, dates and raisins; they differed with regard to other kinds.

b.    
Rikaaz (buried treasure), i.e.,
wealth of the kuffaar buried in the ground that is found by a Muslim. 

Shaykh al-Islam Ibn Taymiyah (may Allaah have mercy on him)
narrated in Majmoo’ al-Fataawa (25/10) that Ibn al-Mundhir (may
Allaah have mercy on him) said: 

The scholars are
unanimously agreed that zakaah is obligatory on nine things: camels, cattle,
sheep, gold, silver, wheat, barley, dates and raisins, if they reach the
nisaab (minimum threshold) for each type at which zakaah becomes due. They
differed with regard to other types of wealth. 

Zakaah for each of these kinds of wealth is obligatory
subject to certain conditions, and a specific amount of the wealth must be
given as defined by sharee’ah. 

See the questions on
zakaah on this site for more
information. 

This zakaah (zakaah on wealth) is one of the five pillars of
Islam. Whoever denies it is a kaafir and whoever withholds it is a
rebellious evildoer; the Muslim ruler must take it from him by force. If he
persists in withholding it and is protected by his tribe then he must be
fought until he pays it. 

Al-Bukhaari (8) and Muslim (12) narrated that ‘Abd-Allaah ibn
‘Umar said: I heard the Messenger of Allaah (peace and blessings of
Allaah be upon him) say: “Islam is built on five (pillars): bearing witness
that there is no god except Allaah, establishing regular prayer, paying
zakaah, fasting Ramadaan and going on Pilgrimage to the House.” 

Al-Bukhaari (25) and Muslim (22) narrated from Ibn ‘Umar that
the Messenger of Allaah (peace and blessings of Allaah be upon him)
said: “I have been enjoined to fight the people until they bear witness that
there is no god except Allaah and that Muhammad is the Messenger of Allaah,
and they establish regular prayer and pay zakaah. If they do that, then they
have protected their blood and wealth from me except in cases where Islamic
laws apply, and their reckoning will be with Allaah.  

The Sahaabah (may Allaah be pleased with them) were
unanimously agreed on fighting those who withheld zakaah. Al-Bukhaari (1400)
and Muslim (20) narrated that Abu Hurayrah (may Allaah be pleased with him)
said: “When the Messenger of Allaah (peace and blessings of Allaah be
upon him) passed away, and Abu Bakr (may Allaah be pleased with him) became
caliph, and some of the Arabs disbelieved and apostatized, ‘Umar (may Allaah
be pleased with him) said: ‘How could you fight the people, when the
Messenger of Allaah (peace and blessings of Allaah be upon him) said,
“I have been enjoined to fight the people until they bear witness that there
is no god except Allaah. Whoever says that has protected his blood and
wealth from me except in cases where Islamic laws apply, and their reckoning
will be with Allaah”?’ Then Abu Bakr said: ‘By Allaah, I will fight those
who separate prayer and zakaah, for zakaah is what is due on wealth. By
Allaah, if they withhold from me a small sheep that they used to give to the
Messenger of Allaah (peace and blessings of Allaah be upon him), I will
fight them for withholding it.’ ‘Umar (may Allaah be pleased with him) said:
‘By Allaah, when I realized that Abu Bakr (may Allaah be pleased with him)
was confident about this idea, then I knew that this was the truth.’” 

With regard to the
zakaah that is obligatory at the end of Ramadaan, this is Zakaat al-Fitr.
The scholars are unanimously agreed that it is obligatory, except those who
held odd views. 

See Tarh al-Tathreeb, 4/46. 

It is less important than the zakaah of wealth with regard to
obligation and status. Zakaat al-Fitr is not one of the pillars of Islam,
and the one who denies it is not a kaafir. 

Zakaat al-Fitr was mentioned in many ahaadeeth, such as the
following: 

Al-Bukhaari (1503) and Muslim (984) narrated that Ibn ‘Umar
(may Allaah be pleased with him) said: The Messenger of Allaah (peace
and blessings of Allaah be upon him) enjoined zakaat al-fitr, a saa’ of
dates, or a saa’ of barley, for every Muslim, slave or free, male or female,
young or old, and he enjoined that it be given before the people go out to
the prayer. 

Abu Dawood (1609) narrated that Ibn ‘Abbaas said: The
Messenger of Allaah (peace and blessings of Allaah be upon him)
enjoined zakaat al-fitr as a purification for those who fasted from idle or
obscene talk, and so as to feed the poor. Whoever gives it before the
prayer, it is accepted zakaah and whoever gives it after the prayer, it is
ordinary charity. Classed as hasan by al-Albaani in Saheeh Abi Dawood. 

See question no. 12459 for more details.