Who is Allah?
Allah is the One true God.
Allah is the Creator of everything.
Allah has no partners and is beyond the limits that he has set for his creation. He is outside of space and time.
Allah has 99 names and each name describes an attribute of Allah; such as Ar-Rahmaan (The Merciful) and Al-Baseer (The All Seeing).
Allah has sent many Prophets to mankind, and they all were sent with the same message, to worship Allah alone.
All praise is due to Allah, The Lord of The Worlds.
The below video by Kamal Saleh from Talk Islam describes who God really is.
The below video by Mufti Menk offers a detailed explanation on who is Allah.
In the below video by One Islam Productions the Shaykh discusses the reality of this world ( the Dunya) to demonstrate Allah's power.