According to piaget's theory of cognitive development, decentration in the concrete operational stage refers to children being able to:

being able to use logic.

In Piaget's theory of cognitive development, in the third stage, Concrete Operational stage, Decentrating refers to the ability of a child to consider multiple aspects of a situation. A child in this stage shows an increase use of logic. 
For example, when asked to choose between two lollipops, the child will have a logical choice because it's going to choose base on the flavor and not colors.