Hey kiddo, do you know what Christian monasticism is? It's when some really dedicated Christians decided to live away from other people and devote their entire lives to God. They did this by following some rules that their leaders made up, and they spent most of their time praying, fasting, and doing other religious activities.
Now, this started way back in the early days of Christianity, even before the year 451. People who lived in monasteries were called monks, and they were usually men who were really serious about their faith. They lived in very basic rooms, and usually didn't have any fancy decorations or possessions. They wore simple clothes, and they didn't eat very much.
Why would someone want to live like this, you might ask? Well, these monks believed that by living this way, they could become closer to God. They thought that by giving up all their worldly possessions and focusing completely on their faith, they could become more holy.
Also, back then, life was really different than it is now. People didn't have smartphones or TVs or anything like that, and there wasn't much to do. So some people just decided to dedicate their lives to God instead.
Before the year 451, there were all sorts of different monastic communities. Some were really strict and had lots of rules, while others were a little more relaxed. But in that year, there was a big meeting of Christian leaders, and they decided to make some official rules about how monasteries should be run. These became known as the "canons" and they were important because they helped create some consistency and organization among the different monastic communities.
So that's what Christian monasticism was like before 451. Does that make sense?