Answer:
Prophet Muhammad called people for full submission (Islam in Arabic) to Allah (god in English) with no partner, no son, no companion, no associate, and no resemblance. It was the call of all prophets since Adam and including Noah, Abraham, Moses, and Jesus (peace be upon them all). He conveyed to his followers the God revelation of Quran, Muslims holy book, to him. He called for good morals, good deeds, following Quran and Sunnah (prophet Muhammad saying and practices), and to follow the Islam five Pillars. Refer to questions below.