A class survey is an activity where all the learners in the group need to ask each other questions to find information, which they then need to analyze and report back to the class.
The class have been reading about things that are bad for their health and now conduct a class survey to find out who in the class has these unhealthy habits. They do this by choosing a question each to ask all the other learners, then collating this information.
In the classroom
Class surveys can have various aims and functions: as warmers, as ice-breakers for new classes, as pre-reading activities, to provide freer practice of target language, as tasks etc. The key qualities of surveys are that they are communicative and dynamic.