Montessori is an educational approach that focuses on allowing children to learn at their own pace, through self-directed activities in a prepared environment [a space that is specially organized for learning]. For example, instead of being taught by a teacher, children in a Montessori classroom might choose an activity to work on, like counting beads or tracing letters.
Very Simple Definition:
Montessori is a way of learning where children get to choose what they want to do and learn in a special classroom. For example, instead of a teacher telling them what to do, they can pick an activity to work on, like counting beads or drawing letters.