This explanation of the immaculate conception is provided at http://www.ncregister.com/blog/jimmy-akin/8-things-you-need-to-know-about-the-immaculate-conception
This article begins
“There’s a popular idea that it refers to Jesus’ conception by the Virgin Mary.
Instead, it refers to the special way in which the Virgin Mary herself was conceived,’”
before this articles goes on to discuss what the immaculate conception means and its effect on Mary herself.
Many Catholics don’t realize the the Virgin Mary said “I am the immaculate conception” when she appeared to Bernadette in Lourdes, France in 1858. See https://catholicismpure.wordpress.com/2013/11/30/i-am-the-immaculate-conception-our-lady-told-st-bernadette/