This sample demonstrates the default functionalities of the SplitButton. By clicking primary button default action will be triggered and clicking secondary button will display popup with list of action items.
The SplitButton component has primary and secondary buttons. Primary button is used to select default action and secondary button is used to toggle contextual overlays for displaying list of action items. It can contain both text and images.
More information about SplitButton can be found in this documentation section.