You can hide and show layers, groups and frames inside instances. This makes it really easy to build components with alternate states or configurations, with some groups of layers hidden by default and later enabled in certain instances.
For example, imagine a “on/off” switch button that has the two states “on” and “off”. You can build a component that includes both those states: one group inside called “on” and another called “off”. Hide the “on” group by default. Now, in any instance of the switch button you can simply un-hide the “on” group to make the instance reflect the “on” state.