How did luther's ideas differ from those expressed by the catholic church?

Martin Luther was primarily opposed to two major things.

The first was the sale of indulgences by the Catholic Church. This was a huge revenue stream wherein you could pay off your sins, no matter how large.

Next, Luther also believed that the Bible alone was the source of divine knowledge and that faith only saved, while the Catholic Church believed in a variety of divinely inspired texts and that faith + good works was the key to salvation.