On this tab, there are two buttons available. The Previous button in the bottom left will take you to Tab 1 if clicked. Inspecting the Properties of that button will show that we are using the Change Tab action and have statically set the target tab to Tab 1. The Next button in the bottom right will take you to the next visible tab in the form. Inspecting the Properties of that button will show that we are using the Change Tab action with Next Tab selected. If Tab 3 is visible when the button is clicked it will be displayed, otherwise the next visible tab will be shown.
The RadioButtons in the middle of the form can be used to show or hide Tab 3. Practice changing the values to show or hide the tab and then inspect the Properties and review the Events tab. If the value selected is "Show Tab 3" the Show Tab action is executed, otherwise the Hide Tab action is executed. Try hiding the tab and then clicking Next to navigate to Tab 4.