Hola, es una festividad religiosa católica, que se celebra en España y en los países hispanohablantes. The anglo saxon culture doesn´t have this celebration, it´s the Epiphany ,or The Three Wise Men´s day,or The three Kings´s Day,the day when the three Kings went to visit Jesus,and brought him presents. So our children get presents twice,for Christmas, and for "Día de Reyes".

"Bajada de Reyes" translates directly into "descent of kings". This could mean the "genealogy of the Royal family" or the "Royal line".