Aggregation implies a relationship where the child can exist independently of the parent . For example, Bank and Employee, delete the Bank and the Employee still exist. whereas Composition implies a relationship where the child cannot exist independent of the parent.
Read moreIS-A relationship in oops?
In OOP, IS-A relationship is completely inheritance . This means, that the child class is a type of parent class. For example, an apple is a fruit. So you will extend fruit to get apple.
Read more