Question: What are the categories of Tawheed (belief in the Oneness of Allaah/Islaamic monotheism)? Is the Muslim required to believe in all these categories? Is it enough for the Muslim to confess Shahaadah (Testimony of Faith)?
Answer: There are three categories of Tawheed which have been defined by means of induction. These categories include Tawheed-ul-Ruboobiyyah (Oneness of Allaah’s Lordship), Tawheed-ul-Uloohiyyah (Oneness of Worship), and Tawheed-ul-Asmaa’ wal-Sifaat (Oneness of Allaah’s Names and Attributes). It is enough for the person to sincerely declare that there is no deity worthy of worship except Allaah (Exalted be He) and that Muhammad is the Messenger of Allaah (peace be upon him). It is the duty of scholars to clarify these religious matters which on which people may be unenlightened. This is based on the fact that the Messenger of Allaah (peace be upon him) accepted those people who testified that there is no deity worthy of worship except Allaah and that Muhammad is the Messenger of Allaah and at the same time they put the words of faith into actual practice. They obeyed the laws of Islaam and declared the Oneness of Allaah (Glorified and Exalted be He). People who declare Shahaadah are called Muslims because Shahaadah means to believe in Allaah as one’s Lord and Creator, and to believe that He Alone is worthy of worship, and to believe in His Names and Attributes. Therefore, to declare that there is no god but Allaah involves belief in the concept of Tawheed-ul-Ruboobiyyah and Tawheed-ul-Asmaa’ wal-Sifaat. Allaah (Glorified be He) is the True God Who is the Lord and Creator of all things. His Being, Names, Attributes and Actions are perfect…. read more here.