Scholars of ‘Aqeeda divide tawhid into four aspects:
Tawhid Ar-Rububiyyah is the tawhid of Lordship. It pertains to Allah’s right as the Lord, and all that entails–the Creator, the Sustainer.
Tawhid Al-Uloohiyyah is the tawhid of worship. It pertains to Allah’s right to be worshipped, without any partners.
Tawhid Al-Asmaa wal Sifat is the tawhid of Allah’s names and attributes–such as that he is Ar-Rahman and Ar-Rahim.
Tawheed Al-Haakimiyyah is the tawhid of legislation that judgement/decree is for Allah alone.
Note that denying part or whole of any of the parts of any of these four is shirk.