The QuestionMark is a feature in SQL Assistant (SQA) to parametrise your SQL. SQA will ask for the value to replace and then Search/Replace the parameter.

In TD Studio by default this feature is deactivated. You can activate it by clicking the "String Substitution" Button of the SQL Editor View. (In my case the 9th Icon on the top right direct to the SQL Text) Unfortunately in some cases the Icon is hidden if you don't make the App FullScreen