Who is G-d, Mommy?

Tonight, like most nights, Ira and I put Abram to bed and we said the Sh'ma. After saying our nightly prayer, Abram turned to me and said, "who is g-d, mommy". I was caught off guard and looked directly at Ira, who proceeded to say "you can take this one". I answered Abram by saying "g-d is someone who protects and looks out for you". Abram seemed ok with that answer, but wanted know more....my response, "we will have to call Rabbi Joui to explain".