Who is martin Luther and why did he speak out against the catholic church in the 1500s?

Martin Luther was a German theologian and a key figure in the Protestant Reformation during the early 1500s. He spoke out against the Catholic Church primarily due to its practices of selling indulgences and perceived corruption, which he believed undermined the core tenets of Christianity. In 1517, he famously posted his Ninety-Five Theses, challenging the Church's authority and advocating for salvation through faith alone, which sparked a significant religious and cultural upheaval in Europe. Luther's actions ultimately led to the establishment of Protestant denominations and a profound transformation in Christianity.