Jibreel (alaihis salam) came in human form and said to Rasul Allah (sal Allahu alaihi wa sallam): “Tell me about true faith (Emaan).” Rasul Allah (peace & blessings o God be upon him) answered: “It is to believe in Allah, His angels, His inspired Books, His messengers, the Last Day, and in destiny, its good and evil.” Jibreel (alaihis salam) said: “You have spoken the truth.” [Sahih Muslim]
Belief in Allah's Books is to believe that the Books of Allah are His Non-created Speech, and that they are sanctified above being comprised of letters and sounds and that everything that they contain is real and true. Four books in particular are:
1) The Tawrah given to Prophet Musa (upon him be the prayer and the peace)
2) The Zabur given to Prophet Dawud (upon him be the prayer and the peace)
3) The Injeel given to Prophet Eesa (upon him be the prayer and the peace)
4) and the Qur'an given to Muhammad (peace & blessings o God be upon him).
Belief in Allah's messengers means to believe that Allah, the Almighty, sent them to His creation for guidance, in order that they would teach them how to perfect their lives in this world and the Hereafter. He aided them with miraculous occurrences that proved their truthfulness. They delivered the message Allah revealed to them. It is obligatory to show respect and courtesy to all of them, and to not distinguish between them (i.e. by saying, "We believe in this one, but we reject this other one.") They are all under Allah's Divine protection from sins great and small.
The number of messengers Allah, the Almighty, sent to humankind is 124,000, and from among them we are required to know 25:
1) Adam 2) Idrees 3) Nuh 4) Hud 5) Salih 6) Ibraheem 7) Lut 8) Isma'il 9) Ishaq 10) Ya'qub 11) Yusuf 12) Shu'aib 13) Harun 14) Musa 15) Dawud 16) Sulaiman 17) Ayyub 18) Dhul Kifl 19) Yunus 20) Ilyas 21) al-Yasa 22) Zakariyyah 23) Yahya 24) Eesa 25) Muhammad (peace & blessings of God be upon them all).
The Muslim should also know that our Prophet Muhammad (sal Allahu alaihi wa sallam) was a Qurayshi Arab, the seal of the prophets and messengers, that he was born in Makkah, that he migrated to al-Madinah, that he died and was buried there, and that the system of law he brought (the Shari'ah) abrogated all systems of law that preceded it, and that it is valid to the Last Day.