Short answers, pulled from the story.
The Abrahamic religions are a set of monotheistic faiths that venerate Abraham as a patriarch or prophet. The three largest are Judaism, Christianity, and Islam; smaller traditions include Samaritanism, the Druze Faith, the Baha'i Faith, and Rastafari.
The term appeared for the first time in the second half of the 20th century. It was introduced to replace the older phrase "Judeo-Christian" in order to include Islam and to acknowledge the differences between Judaism and Christianity.
Christianity has about 2.5 billion adherents (31.1% of the world's population), Islam has about 1.9 billion (24.1%), and Judaism has about 14.1 million. The Baha'i Faith has over 8 million adherents and the Druze Faith has between one million and nearly two million.
Alan L. Berger, professor of Judaic studies at Florida Atlantic University, wrote in 2012 that while the three faiths share ancestry, each tradition views Abraham differently. Aaron W. Hughes describes the term as "imprecise" and "largely a theological neologism", arguing it conceals irreconcilable differences in doctrine and practice.
All three identify the creator of the universe with the God revealed to Abraham and agree that God is eternal, omnipotent, and omniscient. Their religious texts share many of the same figures, histories, and places, though each tradition assigns those figures different roles and meanings.
Islam was founded by Muhammad in the Arabian Peninsula in the 7th century AD and understands its form of Abrahamic monotheism as preceding both Judaism and Christianity. From its founding, Islam conceived of itself as the religion of Abraham, a position derived partly from the Quranic phrase din Ibrahim, meaning the "religion of Abraham".