What is an isolated scope?

In Angularjs, directives by default inherit all the properties from the parent scope, and while creating a custom directive one may need some parent scope properties. There is a possibility that the parent scope at some point in the application lifecycle may get removed/deleted, on the removal of that property the custom directive becomes completely useless.

So to make a custom directive that can access the parent scope properties and at the same time does not rely on it we use isolated scope.