As explained by the Homily on Common Prayer and the Sacraments, in the Church of England’s Second Tome of Homilies (1562):
Cornelius, a devout man, a captain of the Italian army, saith to Peter: that being in his house in prayer at the ninth hour, there appeared unto him one in a white garment &c. (Acts 10.1, 3, 30–31). This man prayed unto God in secret, and was rewarded openly. These be the two private sorts of prayer. The one mental, that is to say, the devout lifting up of the mind to God: And the other vocal, that is to say, the secret uttering of the griefs and desires of the heart with words, but yet in a secret closet, or some solitary place. The third sort of prayer is public or common. Of this prayer speaketh our Saviour Christ, when he saith, If two of you shall agree upon earth upon any thing, whatsoever ye shall ask, my Father which is in heaven shall do it for you, for wheresoever two or three be gathered together in my name, there am I in the midst of them (Matthew 18.19–20). Although God hath promised to hear us when we pray privately, so it be done faithfully and devoutly (for he saith, Call upon me in the day of thy trouble, and I will hear thee (Psalms 50.15). And Elias being but a mortal man, saith Saint James, prayed, and heaven was shut three years and six months, and again he prayed, and the heaven gave rain (James 5.17–18):) Yet by the histories of the Bible it appeareth, that public and common prayer is most available before God, and therefore is much to be lamented that it is no better esteemed among us which profess to be but one body in Christ.