`Father' is a term of address for priests in some churches (especially the Roman Catholic Church or the Orthodox Catholic Church); `Padre' is frequently used in the military
<noun.person>
Padre \Pa"dre\ (p[aum]"dr[=a]), n.; pl. Sp. & Pg. {Padres} (p[aum]"dr[=a]s); It. {Padri} (p[aum]"dr[=e]). [Sp., Pg., & It., fr. L. pater father. See {Father}.] 1. A Christian priest or monk; used as a term of address for priests in some churches (especially Roman or Orthodox Catholic in Italy, Spain, Portugal, and Spanish America); -- also used in the American military.
Syn: Father. [Webster 1913 Suppl.]
2. In India (from the Portuguese), any Christian minister; also, a priest of the native region. --Kipling. [Webster 1913 Suppl.]
3. A chaplain in one of the military services.
Syn: military chaplain, Holy Joe, sky pilot. [WordNet 1.5]