The Month of June is dedicated to the Sacred Heart. The Church celebrates the Solemnity of the Sacred Heart of Jesus on the Friday following the second Sunday after Pentecost. In addition to the liturgical celebration, many devotional exercises are connected with the Sacred Heart of Jesus. Of all devotions, devotion to the Sacred Heart was, and remains, one of the most widespread and popular in the Church.
Understood in the light of the Scriptures, the term "Sacred Heart of Jesus" denotes the entire mystery of Christ, the totality of his being, and his person considered in its most intimate essential: Son of God, uncreated wisdom; infinite charity, principal of the salvation and sanctification of mankind. The "Sacred Heart" is Christ, the Word Incarnate, Saviour, intrinsically containing, in the Spirit, an infinite divine-human love for the Father and for his brothers.
—Excerpted from the Directory on Popular Piety and the Liturgy