Data binding is a widely used concept inside Toolpad apps. It allows connecting various parts of the application and make them react to data changes.
In order to initiate data binding look around in the UI for a binding button.
The easiest way to tell if a value can be "data bound" is by locating binding button, i.e. TextField component allows us to bind every property that we could otherwise control manually.
At the top of the editor you can see an explanation what type of property we expect to be defined (i.e. above mentions string).
On the left side of the editor you have a list of all the variables in the scope that can be used to define the expression.
All that's left is to click Update binding and you can observe how application behaves.
(In this example you can see TextField value bound to the value of Typography component).
Field with value: