Difference between nazm and ghazal in Urdu poetry

A friend of mine recently mailed me this poem of the great Urdu poet Faiz, and asked me whether it was a nazm or a ghazal. He also asked the meaning of the difficult words therein

Bahaar aayi to jaise yak-baar
Laut aaye hain phir adam se
Woh khwaab saare shabaab saare
Jo tere honton pe mar-mite they
Jo mit ke har baar phir jiye they
Nikhar gaye hain gulaab saare
Jo teri yaadon se mushkboo hain
Jo tere ushhaaq ka lahoo hain
Ubal pade hain azaab saare
Malaal-e-ahwaal-e-dostaan bhi
Khumaar-e-aaghosh-e-mahv-e-shaan bhi
Ghubaar-e-khaatir ke baab saare
Tere hamaare
Sawaal saare jawaab saare
Bahaar aayi to khul gaye hain
Naye sire se hisaab saare

This was my reply to him:

This is a nazm, not a ghazal.
There are two basic differences between a nazm and a ghazal :
Firstly, in a nazm there is a single theme or topic throughout the poem, whereas in a ghazal each sher (couplet ) in it is independent, and a condensation of a complete idea, which may have nothing to do with neighbouring ones in the ghazal

Secondly, a ghazal must strictly follow the rules of (1) radeef (2) qaafiya (3) beher (4) matla and (5) maqta, while a nazm may or may not do so.

To explain these rules, let me give an example :

Take Faiz’ ghazal which begins with this sher:

” Gulon mein rang bhare baad-e-naubahaar chale
Chale bhi ao ki gulshan ka kaarobaar chale ”

(1) Radeef is the last word or words in a line in a poem ( called a misra ), which have to be identical in the first sher of the ghazal.

In the above sher ‘chale’ is the radeef.
In the first sher of the ghazal both lines ( misras ) must have the radeef. However, in succeeding shers, only the second misra in the sher must have it. For example, in the above ghazal, the second sher is :

” Qafas udaas hai yaaron saba se kuch to kaho
Kaheen to beher-e-khuda aaj zikr-e-yaar chale ”

One may notice that here the last word in the first line is not ‘chale’ but ‘kaho”. Only the second line ends with the radeef ‘chale’. Similarly, the succeeding shers in the ghazal have the radeef ‘chale’ only in the second line.

(2) Now let me explain qaafiya.
Qaafiya is the word ( or words ) preceding the radeef. It must be rhyming, but need not be identical ( which a radeef must be ).

To understand this, consider the first sher in the above ghazal.
One will notice that before the radeef ‘chale’ there are rhyming words in both misras of the sher, that is, ‘naubahaar‘ and ‘kaarobaar‘.

In the second sher of the ghazal ( and in succeeding shers ), the qaafiya must only be in the second misra, and need not be in the first ( as is the requirement for radeef ).
Thus the qaafiya in the second sher is ‘yaar’, which rhymes with ‘naubahaar’ and ”kaarobaar’. All succeeding shers in this ghazal have the qaafiya in the second misra. The last sher in the ghazal ( which is called maqta, and in which the pseudonym of the poet usually appears ) is :

” Maqaam Faiz koi raah mein jacha hi nahi
Jo koo-e-yaar se nikle to soo-e-daar chale ”

Here the qaafiya is ‘daar’ which rhymes with the qaafiyas in all earlier shers.

(3) Beher means metre. Urdu verses may have different metres, but in a ghazal, the same metre must strictly be observed throughout. The poet is not free to have one kind of metre in one sher, and another in other shers in the same ghazal.

(4) Matla is the first sher ( couplet ) in a ghazal, and it is distinguished from succeeding shers in the ghazal in that in both its misras there is radeef and qaafiya

(5) Maqta is the last sher in a ghazal, and it usually includes the pseudonym ( takhallus ) of the poet.
Now as regards the particular nazm you sent me. Here is a translation :
https://qausain.wordpress.com/2009/11/22/bahar-aai-to-jaisay-faiz-ahmed-faiz/
The meaning of the words in it are :
1.Yekbaar=once again
2. Adam =non existence, other world
3.Shabaab =youth
4. Nikhar=fresh, clean
5.Mushkboo=fragrant
6.Ushshaaq =lovers ( it is plural of aashiq )
7.Azaab=difficult
8.Malaal-grief
9.Ahvaal=condition
10. Khumaar=intoxication
11. Aagosh=lap
12. Mehveshaan=drunk
!3. Ghubaar=mist
!4. Khaatir= memory ( khaatir also means for the sake of, or hospitality )
15. Baab=door

The poem you have mentioned is a nazm, not a ghazal, because (1) a single theme pervades the entire poem (2) the rules of ghazal ( mentioned above ) have not been strictly followed

I hope this helped