The word hijab is originated from an Arabic word hajaba means to hide or cover. Muslim women observe hijab as ALLAH has ordered them to do so. In the Holy Quran the term jilbab and Khymar is also used in relation with hijab.
Hijab is a compulsion for Muslim women
In Islam there is no specific clothing defined for Muslim women but there are some specific instructions about how to dress up. The cloths should be loss enough through which there body parts are not being highlighted then they should not wear hazy and shiny cloths which would attract a men’s attention but there is a compulsion that every Muslim should observe hijab as this is clearly stated in the verse of the Holy Quran

"O Prophet, tell your wives and daughters and the believing women to draw their outer garments around them (when they go out or are among men). That is better in order that they may be known (to be Muslims) and not annoyed..."
[Qur'an 33:59]

One of the reasons why Muslim women are told to observe hijab is clearly stated in the verse that because of hijab Muslim women would differentiate themselves from non Muslims. Another reason to observe hijab is to keep a difference between men and women. Muslim women observe hijab so that people will judge them on the basis of their skills not on the basis of their looks and appearances. Hijab also protects a woman as she hides her appearance from men so no one could think about her sexuality. That is why a woman in hijab is considered to be a pure, virtuous Muslim woman who has a strong and good moral character.

Great Islamic conquests
The great Islamic conquest started in between AD 632 and 750.After the death of prophet (pbuh) this conquest were started Muslim are in shocked because of the death of are holy prophet. In order to ease their doubts, one among Mohammed's chief followers, Abu Bakr self-addressed the group gathered in Mecca: "Whichever of you worships prophet, recognize that prophet is dead. But whichever of you worships God, recognize that God is alive and doesn't die.
The first Islamic conquest
The first major conquest, noted for its brutality, occurred in Arabia itself, like a shot once Muhammad's death in 632. several tribes that had only nominally accepted Islam's authority, upon Muhammad's death, patterned they might break away; but, Muhammad's successor and 1st caliph, or successor, Abu Bakr, would have none of that, and declared a jihad against these peoples, because the "Ridda Wars" (or Apostasy Wars). In step with the said historians, tens of thousands of Arabs were place to the steel till their tribes re-submitted to Islam. The Ridda Wars is over around 634 to stay the Arab Muslims from quarreling, succeeding kaliph, Omar, launched the Muslim conquests: Syria was conquered around 636, Egypt 641, geographic region and therefore the Persian Empire, 650. By the first eighth century, all of North Africa and European country to the west, and therefore the lands of central Asia and Asian country to the east were conjointly brought below Muslim suzerainty.
Act of Muslims in Islamic conquest
The Muslims of Islamic conquests are seen as acts of altruism: they're remarked as futuh, which accurately suggests that "openings" that is, the countries conquered were "opened" for the sunshine of Islam to enter and guide its pagan inhabitants. Therefore to Muslims, there's nothing to regret or apologize for regarding the conquests; they're seen as for the great of these who were conquered. The Islamic conquests narrated within the Muslim histories usually mirror the belief obligations set go into Islam's system of rules texts the al-Qur'an and Hadith.