Tawhid can be explained in simple terms as most muslims understand or, be explained in a spiritually advanced level.
To most of our muslims, Tawhid means the Oneness of Allah. They will swear that Allah is One; The Greatest & Most Powerful; the Giver & Taker of Life; He doesn’t beget nor can he be begotten!
Then, they will quickly move to assign limits to Allah’s Omnipotence! What He can be or cannot be! Imagine, His creations assigning limits to Allah! To me that would be Shirk, Kufr, Heresy, all rolled into one.
Tawhid can also be explained in a higher level of spirituality, mysticism & gnosticism. To them, Tawhid is explained by this quote from a Sufi mystic,Ibn Arabi:
“If the believer understood the meaning of the saying ‘the color of the water is the color of the receptacle’, he would admit the validity of all beliefs and he would recognise God in every form and every object of faith.”
Most of our muslims would call this KUFR, let alone shirk and, be-head the bloody b…!
So, my friend - how dare we assign limits to the limitless Allah?