What is Islam, and what do Muslims believe?

In the name of God, the Most Gracious, the Most Merciful  (بِسْمِ اللهِ الرَّحْمٰنِ الرَّحِيْمِ)   

Lets Start learn more about islam and the Muslims. (i got this article from here)

Islam is a religious system begun in the seventh century by Muhammad (peace be upon him). Muslims follow the teachings of the Qur’an and strive to keep the Five Pillars.

The History of Islam
Islam is not a new religion but bestowed from god to Adam (peace be upon him) and continue do be perfected and finally, Muhammad (peace be upon him) claimed the angel Gabriel visited him. During these angelic visitations, which continued for about 23 years until Muhammad's death, the angel purportedly revealed to Muhammad the words of Allah (the Arabic word for “God” used by Muslims). These dictated revelations compose the Qur'an, Islam's holy book. Islam means “submission,” deriving from a root word that means “peace.” The word Muslim means “one who submits to Allah.”

The Doctrine of Islam
Muslims summarize their doctrine in six articles of faith:

1. Belief in one Allah: Muslims believe Allah is one, eternal, creator, and sovereign.
2. Belief in the angels. 
3.  Belief in the prophets: The prophets include the biblical prophets but end with Muhammad as Allah’s final prophet. 
4. Belief in the revelations of Allah: Muslims accept certain portions of the Bible, such as the Torah, and 1500 years old Gospel of Barnabas (in the Ethnography Museum of Ankara Turkey) as they only believed in God original word. They believe the Qur'an is the preexistent, perfect word of Allah. 
5. Belief in the last day of judgment and the hereafter: Everyone will be resurrected for judgment into either paradise or hell.

The Five Pillars of Islam
These five tenets compose the framework of obedience for Muslims:

1. The testimony of faith (shahada): “la ilaha illa allah. Muhammad rasul Allah.” This means, “There is no deity but Allah. Muhammad is the messenger of Allah.” A person can convert to Islam by stating this creed. The shahada shows that a Muslim believes in Allah alone as deity and believes that Muhammad reveals Allah.
2. Prayer (salat): Five ritual prayers must be performed every day.
3. Giving (zakat): This almsgiving is a certain percentage given once a year.
4. Fasting (sawm): Muslims fast during Ramadan in the ninth month of the Islamic calendar. They must not eat or drink from dawn until sunset.
5. Pilgrimage (hajj): If physically and financially possible, a Muslim must make the pilgrimage to Mecca in Saudi Arabia at least once. The hajj is performed in the twelfth month of the Islamic calendar.

A Muslim's entrance into paradise hinges on obedience to these Five Pillars. Still, Allah may reject them. Even Muhammad was not sure whether Allah would admit him to paradise (Surah 46:9; Hadith 5.266).

An Evaluation of Islam
Compared to Christianity, Islam has some similarities but significant differences. Like Christianity, Islam is monotheistic. However, Muslims reject the Trinity—that God has revealed Himself as one in three Persons: the Father, Son, and Holy Spirit.

Muslims claim that Jesus (peace be upon him) was one of the most important prophets—not God’s Son. Islam asserts that Jesus (peace be upon him), though born of a virgin, was created like Adam (peace be upon him). Muslims do not believe Jesus (peace be upon him) died on the cross. They do not understand why Allah would allow His prophet Isa (the Islamic word for "Jesus") (peace be upon him) to die a torturous death. Yet the Bible shows how the death of the perfect Son of God was essential to pay for the sins of the world (Isaiah 53:5-6; John 3:16; 14:6; 1 Peter 2:24).

Islam teaches that the Qur'an is the final authority and the last revelation of Allah. The Bible, however, was completed in the first century with the Book of Revelation. The Bible warns against anyone adding to or subtracting from God’s Word (Deuteronomy 4:2; Proverbs 30:6; Galatians 1:6-12; Revelation 22:18). The Qur’an, as a claimed addition to God’s Word, directly disobeys God’s command.

Muslims believe that paradise can be earned through keeping the Five Pillars. The Bible, in contrast, reveals that sinful man can never measure up to the holy God (Romans 3:23; 6:23). Only by God’s grace may sinners be saved through repentant faith in Jesus (Acts 20:21; Ephesians 2:8-9).

Because of these essential differences and contradictions, Islam and Christianity cannot both be true. The Bible and Qur’an cannot both be God’s Word. The truth has eternal consequences and Muslims believe Qur'an will never changed, and until now no one have ever found a single mistake from every information that is written in the Qur'an.

“Beloved, do not believe every spirit, but test the spirits to see whether they are from God, because many false prophets have gone out into the world. By this you know the Spirit of God: every spirit that confesses that Jesus Christ has come in the flesh is from God; and every spirit that does not confess Jesus is not from God; this is the spirit of the antichrist, of which you have heard that it is coming, and now it is already in the world” (1 John 4:1-4; see also John 3:35-36).

You can find The Qur'an translation here.

so, anybody who interested to know more could upvote and i'll try to keep updating more about islam as muslim myself. If you have a question, just ask, i'll try to answer it within my knowledge cause we're all learning here.