PARDAH :

1) Veil of the eyes :

The very first step of parda is “Aakhon ka parda” that means namehram men and women should bow their eyes whenever either of them are across each other.
In Chapter 24, known as an-Nur (the Light), in verse 30, Allah commands Prophet Muhammad as follows:

قُلْ لِلْمُؤْمِنِيْنَ يَغُضُّوْا مِنْ أَبْصَارِهِمْ وَ يَحْفَظُوْا فُرُوْجَهُمْ, ذَلِكَ أَزْكَى لَهُمْ.

“Say to the believing men that: they should cast down their glances and guard their private parts (by being chaste). This is better for them.”(24:30).

قُلْ لِلْمُؤْمِنَاتِ يَغْضُضْنَ مِنْ أَبْصَارِهِنَّ وَ يَحْفَظْنَ فُرُوْجَهُنَّ…  

    
“Say to the believing women that: they should cast down their glances and guard their private parts (by being chaste)…” (24:31).

2) Veil of the house :

Second step is ” Ghar ka parda” i.e who should be allowed to enter home and who should be barred .

‏ يٰۤـاَيُّهَا الَّذِيۡنَ اٰمَنُوۡا لَا تَدۡخُلُوۡا بُيُوۡتًا غَيۡرَ بُيُوۡتِكُمۡ حَتّٰى تَسۡتَاۡنِسُوۡا وَتُسَلِّمُوۡا عَلٰٓى اَهۡلِهَا ؕ ذٰ لِكُمۡ خَيۡرٌ لَّـكُمۡ لَعَلَّكُمۡ تَذَكَّرُوۡنَ‏

Believers! Enter not houses other than your own houses until you have obtained the permission of the inmates24 of those houses and have greeted them with peace. This is better for you. It is expected that you will observe this.

3) Veil of the woman :

In Islam women are looked upon as an idol of grace and elegance. Unlike men she is not treated as rough and tough. It is said in Islam ” A women should be treated as fragile “( but remember she is not fragile) . So in that respect, it has been asked women to maintain the aura and modesty, by covering herself entirely so that no random person ( namehram be it a male or a female) could come across and get entertained after observing her beauty.

وَ لاَ يُبْدِيْنَ زِيْنَتَهُنَّ إِلاَّ مَا ظَهَرَ مِنْهَا وَ لْيَضْرِبْنَ بِخُمُرِهِنَّ عَلىَ جُيُوْبِهِنَّ…
“…and not display their beauty except what is apparent, and they should place their khumur over their bosoms…” (24:31).

THE SIX POINT CRITERIA FOR PARDAH :

Based on the Qur’an and Sunnah (the teachings of the prophet Muhammad peace be upon him) there is a six point criteria for observing hijab correctly:

The first criterion is the extent of the body that should be covered. This is different for men and women. The extent of covering obligatory on the male is to cover the body at least from the navel to the knees. For women, the extent of covering obligatory is to cover the complete body except the face and the hands up to the wrist. If they wish to, they can cover even these parts of the body.
All the remaining five criteria are the same for men and women.

The clothes worn should be loose and should not reveal the figure.
The clothes worn should not be transparent such that one can see through them.
The clothes worn should not be so glamorous as to attract the opposite sex.
The clothes worn should not resemble that of the opposite sex.
The clothes worn should not resemble that of non-Muslims i.e. they should not wear clothes that are specifically identities or symbols of other religions.
Hijab includes conduct and behaviour among other things. Complete ‘hijab’, besides the six criteria of clothing, also includes the moral conduct, behaviour, attitude and intention of the individual. A person only fulfilling the criteria of ‘hijab’ of the clothes is observing ‘hijab’ in a limited sense. ‘Hijab’ of the clothes should be accompanied by ‘hijab’ of the eyes, ‘hijab’ of the heart, ‘hijab’ of thought and ‘hijab’ of intention. It also includes the way a person walks, the way a person talks, the way he behaves, etc.

In conclusion, the hijab is a protection for both men and women.