When information is consistent with a schema, it is assimilated into the schema. For example, a child's schema for an apple may be an edible, green, hard sphere. Every time the child sees a green apple, the experience is assimilated and the schema is strengthened.
When the information is inconsistent with a schema, accommodation occurs and the schema has to change in order to resolve the problem. SO if a child sees a red apple, their apple schema has to accommodate this new information - it becomes an edible, hard sphere that is either green or red.