"Year A" homilies and sermons are reflective commentaries that a priest or pastor gives following a reading from the Gospel of Matthew. Most people consider homilies and sermons to be one in the same, providing a clearer understanding of the scripture for the laity during Christian celebration.
The Second Vatican Council of 1962-1965 reorganized the lectionaries for Sunday readings at mass into three-year cycles. "Year A" focuses on the Gospel of Matthew, "Year B" focuses on the Gospel of Mark and "Year C" focuses on the Gospel of Luke. This lengthened schedule allows Catholics the opportunity to better understand the text of the Bible, as opposed to the previous one-year lectionary schedule.