Simplify the following definition
The sensorimotor stage, from birth to two years old, is characterized by infants exploring the world through sensory observation and motor functions. They are egocentric and learn to manipulate their surroundings using their senses. The goal of this stage is to develop object permanence, where children realize that objects exist independently of their interactions with them. Symbolization occurs when infants can visualize an object mentally regardless of its physical location.