Variable overrides enable you to override variable default values for composite components. They cannot be used for simple components.
When a component contains other components, called child components, variable settings only affect the top-level parent component. All child components use the default values for their variables. A child component can obtain variable values from its parent component in these two ways:
The container (parent) component “pushes” variable values to the contained (child) components. To override the default values for child components, set the variable overrides when you create a component that contains child components. Each referenced component has a set of variable overrides that you can use.
The contained (child) components “pull” variable values from the container (parent) component. One or more of the contained component's variable values are defined based on the value of a variable in the container component. The contained component uses the variable substitution syntax :[container:varname] in the default value of its variables.