This is the term for a form you give to a potential participant in a research study to have them answer some questions. It's a lot like a survey in terms of functionality, but the main difference is that you, as someone that wants to get the participants, reads each screener response individually to get a feel for that person. Surveys are usually more about aggregate data collection and analysis. Screeners are more about having both open and closed-ended responses. Here's an example:
Ethnio also offers various screener designs and customization options.