Christians and Muslims both speak of God, but their understanding is very different.
In Islam, Allah is seen as one God, but He is distant. Muslims believe in obeying His commands, but there is no guarantee of forgiveness or closeness with Him. He is not seen as a Father.
In Christianity, God is one but exists as Father, Son, and Holy Spirit. This is the Trinity. God is not distant but personal. He loves people and invites them into a relationship with Him.
Another difference is Jesus. In Islam, Jesus is only a prophet. In Christianity, Jesus is God Himself who became man, died for sins, and rose again. This changes everything.
Christianity also teaches salvation by grace, not by works. Muslims hope their good deeds will outweigh their bad, but Christians trust fully in what Jesus has already done.
So while both religions believe in one God, the Christian God is revealed as loving, personal, and present in Jesus Christ. That makes Him very different from Allah.