The Prophet is one who receives revelation from God through angle jibrael(Gibrael). Prophet Mohammed (Pbuh) is the last prophet on the earth, his religion Islam is the latest religion. And the latest must be adopted. Some people say bahai and sikhism to be so called religions. But it is wrong. The founders Bahaullah and Guru Nanak were not Prophets. Their book is not descended through angle jibrael. So, we can call it as sects. Their book is hand written just like uncounted number of saints in Islam who wrote their own books and they had their own followers. But we call then as a branch of a religion.