A Montessori Dictionary has many of the terms you need to understand Montessori in practice and theory. Here is an example:

“Three Hour Work Cycle
Through years of observation around the world, Montessori came to understand that children, when left in freedom, displayed a distinct work cycle which was so predictable it could even be graphed. This cycle with two peaks and one valley lasted approximately three hours. In Montessori schools children have three hours of open, uninterrupted time to choose independent work, become deeply engaged, and repeat to their own satisfaction. “