“Purification of the six roots (of senses)” means that when our eyes sees objects, those objects’ physical appearances will not result in any sort of emotions in us.
When our ear hears sounds of the world, the sounds do not move us. Our nose is not moved by worldly smells; our tongue is not moved by worldly flavours; our body is not moved by worldly touches; our mind (or thoughts) are not moved by worldly conducts or behaviours.
To not be moved by our surroundings or the environment, is known as Samadhi in buddhist term; it is a state of intense concentration achieved through meditation or being highly focused.
To achieve intense concentration does not necessarily mean having to sit and meditate. Through moving (walking and actions), stillness (standing or not moving), sitting and lying down, one can also still be in meditation.
It does not mean that when one is in the stage of meditation, he will be like a wooden block or clay, not being aware of everything else around him. Instead, he will still be in tune with all things, except he is not at all affected by his awareness.
This is where one is still able to make changes to his surroundings and situations and is in turn not changed or controlled by the surroundings and situations he is in. It is also known as one being able to change his surroundings and not be changed by it.
Extracted from: Venerable Master Xuan Hua《Dharma World Buddhist Federation Buddhism Studies and Common Questions》