This is a Marian antiphon, which is a type of commonly sung Latin prayer that concludes other devotions. It is common to sing the Latin version even in an English prayer just because the Latin songs are very traditional.
Hail, Holy Queen, Mother of mercy, our life, our sweetness, and our hope. To thee do we cry, poor banished children of Eve. To thee do we send up our sighs, mourning and weeping in this valley of tears. Turn then, most gracious advocate, thine eyes of mercy toward us. And after this our exile, show unto us the blessed fruit of thy womb, Jesus. O clement, O loving, O sweet Virgin Mary.
Salve, Regina, mater misericordiae, vita, dulcedo, et spes nostra, salve. Ad te clamamus, exsules filii Hevae. Ad te suspiramus, gementes et flentes in hac lacrimarum valle. Eia ergo, advocata nostra, illos tuos misericordes oculos ad nos converte. Et Iesum, benedictum fructum ventris tui, nobis post hoc exsilium ostende. O clemens, O pia, O dulcis Virgo Maria.