Most formulas calculate a value. Like an Excel spreadsheet, recalculation happens automatically as values change. For example, you might want to show the value in a Label control in red if the value is less than zero or in black otherwise. So you can set the Color property of that control to this formula:
If( Value(TextBox1.Text) >= 0, Color.Black, Color.Red )
By selecting a Button control, the user initiates a sequence of actions, or behaviors, that will change the state of the app:
Because these functions change the state of the app, they can't be automatically recalculated. You can use them in the formulas for the OnSelect, OnVisible, OnHidden, and other On... properties, which are called behavior formulas.
Use semicolons to create a list of actions to perform. For example, you might want to update a context variable and then return to the previous screen:
Actions are performed in the order in which they appear in the formula. The next function won't start until the current function has completed. If an error occurs, subsequent functions might not start.