How was Mass celebrated in the Middle Ages? What was in Latin, what was in the vernacular? Do the priests actually preach in the Catholic Church, or is it only about the eucharist? And did they do so back then, too?
How much could the average Catholic layman understand? How was he instructed/taught about the faith?
The usual Protestant charicature is, that once a week everyone would go to Church where everything was in latin and noone understood anything. Then they would go home, still ignorant of the Christian faith.
Obviously, the picture that you have painted is erroneous. I would like to recommend three authors that might help you get to the bottom of your questions. The first would Joseph A. Jungmann S.J. The second would be Adrian Fortescue. They are both premier scholars and authors who have written extensively about the Sacred Liturgy throughout history. The third author would be Michael Davies whose works are very easy to come by and are very accurate.
“The Middle Ages” is a bit vague. What time period are you referring to and where?
There were a number of different Rites-- such as the Ambrosian (of St. Ambrose), the Sarum in England, etc. The Latin Rite that reformed at Trent was the main Rite.
Latin was the language of the educated. Prayers were in Latin and the people knew their prayers, even the illiterate. The priests taught them their prayers.
Do you mean now? Of course priests preach. Have you never been to a Mass?
Of course they did.
They knew their prayers. Homilies would be in the vernacular.
That varied widely from place to place, century to century, and from class to class.
I don’t think one answer can be given for this question. Perhaps you can read some of Regine Pernoud or William Carroll’s books on the history of the Church to gain a better understanding.
Mass was said daily, and additionally the Liturgy of the Hours prayed. Many lay people attended Mass daily and also prayed prayers of the Hours. Moreso the upper class. But, the Church also had the lower classes attending Masses frequently-- as a way to ensure they were not overworked by their lords.
The whole of society revolved around the Church. It was an integral part of everyone’s lives-- the holy days, feast days, devotional practices, mass, daily prayers, etc.
Clearly you have studied no history or you would not be asking this particular question.