Generalization refers to the transfer of a skill that is learned in one environment or situation to another environment or situation without explicit teaching.
Example: Completion of puzzle. Child learns to complete a puzzle in school. Generalization has occurred when the child completes that puzzle along with others, in various settings including other classrooms, the cafeteria, the home setting, and in the presence of various teachers, peers, therapists and/or parents in the home setting.
Children typically learn incidentally, by watching others. When they learn a skill in typical fashion they ordinarily master the skill and are able to display the skill across various settings and in the presence of various individuals.
Sometimes children need a more structured style of teaching in order for them to learn. Often those same individuals will need further guidance to begin to display those skills across various settings, utilizing various materials, and in the company of various individuals.
When you are teaching your child to generalize skills, you are teaching them to exhibit skills they have learned in one setting with one person, across various settings and people. The goal of generalization should be taken in to consideration upon the inception of a skill.