Monks are people devoted to being closer to God by service, obedience and poverty. Many of their orders have been cloistered and set far apart from the world. In order to practice their religious devotion, they build monasteries where they can live and worship God. Each monastery has at least a chapel or church where religious services are held. While they are not priests, they still attend mass on a regular basis. Priests often have the duty of visiting the local monasteries to perform mass for the monks.
There are a number of different orders of monks. Each order has its own priorities and chooses how their vows will be achieved. Some take vows of silence. Others do good works for local communities. Some have chosen study as their way to get closer to God. These are the monks that helped preserve much of the scholarship that armies tried to destroy during the Dark Ages.
While all monasteries have churches or chapels for services, not all churches have monasteries. Many churches stand alone and have no other structures on their grounds except for the buildings where the priests are housed. Monasteries have long been kept isolated. This enables the monks to spend their days worshipping and praying. It allows them to follow their religious vows with little interference from the outside world.
Few orders of monks welcome visitors. This is because visitors would interfere with their religious works and prayer routines. There are some that have occasionally given refuge to people from outside in times of war or political strife. Orders that have chosen to preserve knowledge have often housed scholars not associated with their order. Part of their work is to not only preserve knowledge, but to allow others access to it. They preserve knowledge of Christian culture in order to spread it should the Dark Ages once again encroach upon humanity.