Tawheed means Oneness and Uniqueness of Allah.
Islam is an Arabic word, which comes from the word ‘Salm’ which means peace and from 'Silm', which means submitting your will to Allah. Islam believes in 'Tawheed' which is not merely monotheism i.e. belief in one unique God, but much more. Tawheed literally means "unification" i.e. "asserting oneness" and is derived from the Arabic verb 'Wahhada' which means to unite, unify or consolidate. Tawheed can be divided into three categories.
(i) Tawheed ar-Ruboobeeyah (maintaining the unity of Lordship).
(ii) Tawheed al-Asmaa-was-sifaat (maintaining the unity of Allah's name and attributes).
(iii) Tawheed al-Ibaadah (maintaining the unity of worship).