In your web screens you can present an expression with a value that is computed at run-time and can use data from the eSpace. This behavior is implemented by the Expression widget .
An expression is a combination of values and operators or it can be the result of a function. In Service Studio you have a specific editor to handle expressions; however, you can just type the expression in its Properties window.
You can convert a Expression widget to a Link. How?
The maximum length of an expression is 50 Kb; Service Studio performs this evaluation at development time.
Expression Widget Properties | Apply Styles | Un-escaped Expressions