Allāh الله is simply the Arabic word for “The God.” This is the God of Abraham. Christians speaking Arabic would say Allah for God.
Likewise Yahweh, a form of the Hebrew name of God used in the bible. The name came to be regarded by Jews as too sacred to be spoken but it is the same God as mentioned in the Quran.
The God of Abraham includes Jews, Christians, and Muslims. The lineage for Jews and Christians comes under Isaac and for Muslims under Ismael. Both are the sons of Abraham. This is profoundly misunderstood by non-Muslims and Muslims alike.