Here you'll find everything related to Button Actions on NowButtons.com. You can access the web app via https://app.nowbuttons.com.
Actions are the behaviors of your buttons. A single button can do many things, e.g. start a call or send an email. In these buttons, the actions are phone and email.
The Single Button is a single action button.
The Multibutton and the Buttonbar are multi-action buttons.