How does Islamic religion affect people and how does it spread?

Answer 1

The Islamic religion affects people in two directions:

1. performing Ritual worships
2. performing Social and moral practices

For more details, one is referred to related questions below.

Answer 2

The following points are some highlights regarding to this fact :

1. The prophet Muhammad PBUH is the prophet of Islam & the first & most important teacher for Muslims.He is the teacher of all the ethics, morals,principles & rules of Islam & He is the one who received the last revelations from Allah to the mankind "The Holy Quran" which is the Constitution of Islam. Consequently He is the one who had established the Islamic Culture & Civilization from the beginning.

2. Muhammad PBUH established the first Islamic Community in Al-Madeenah (Yathreb) after His migration from Mecca , this community is the sample community for all His companions who established similar communities in many spots on the Earth other than the Arabic Peninsula.

3. The message of Islam is universal, believes in equality between all people & accepts them from all over the world regardless to their races, languages..etc.

please, see the related question for more details about this point.

4. After the Treaty of Hudaybiyyah Muhammad PBUH decided to send serious, wise & kind letters to many rulers of the world, inviting them to Islam. Muhammad, according to the Islamic history, sent ambassadors with such letters to Heraclius the emperor of Byzantium, Chosroes II the emperor of Persia, the Negus of Ethiopia, Muqawqis the ruler of Egypt, Harith Ghassani the governor of Syria ( Particulary South of Jordan now), Munzir ibn sawa Al Tamimi the ruler of Bahrain.

Allah says in the Holy Quran :

"We have not sent thee but as a universal (Messenger) to men, giving them glad tidings, and warning them (against sin), but most men understand not."

(Holy Quran :Chapter 34 : verse 28)Saba' (Sheba)