Fundamentals of Islam

Tawheed - (Oneness of God) - It means believing that God is One. He has neither a colleague nor a partner. He begets not, nor is He begotten, and there is none like Him.
'Adl - (Justice) - Essentially part of Tawheed. Belief that God is Just. He will reward or punish any person according to his deeds and thus the notion of predestination (where all decisions are God's and not any one else's) in one's deeds does not exist.
Nubuwwat - (Prophethood) - Belief in the Prophets (PBUT) of God who excel all other persons for whom they are sent for. A Prophet is sinless (ma'soom). Prophet Muhammad Mustafa (PBUH&HF) is the last of the prophets sent by God. The total number of prophets (PBUT) that were sent by God to mankind is 124,000 and every nation on earth was given guidance through them.
Imamat - (Guidance) - Essentially part of Nubuwwat. Belief that prophethood ended with Prophet Muhammad (PBUH&HF). Then God deputed Imams (leaders) to guide us. They are sinless (ma'soom). The Imams have knowledge from God, and their verdict is the verdict of God. Imams are twelve and they are the only rightful leaders and successors of the Holy Prophet (PBUH&HF). There is no successor to the Twelfth Imam Muhammad ibnul Hassan (PBUH) who is alive today but is in hiding.
Qiyaamat - (Resurrection) - Belief in the Day of Judgement when all human beings shall be raised from the dead and all their good and bad deeds shall be ultimately judged and recompensed accordingly.

From Know Your Islam by Yousuf N. Lalljee