Yes, it's true that until very recently the LDS Church would not admit Black men to the priesthood, priesthood being something every Mormon man participates in. It's something like confirmation or Bar Mitzvah to compare it to other religious traditions. The ban was based on Biblical and Book of Mormon references to people of African descent being the children of Cain or Ham, and therefore cursed. Lacking the right to be "priests," Black men were essentially excluded from participation in LDS Church life, including going on missions and entering temples.

The ban stayed in place until 1978, when Mormon leaders lifted it, saying they had received direct revelation from God that they should. The Church has never, however, apologized for its racist practices prior to 1978, and recent surveys indicate that something like 80% of Mormons believe the ban was inspired by God and therefore appropriate before 1978.

Which is ... well, stunning.

But at least the 1978 action (like the much earlier action disavowing polygamy) shows the Church can and will change basic doctrine when they want to.