Fieldwork is a market research term which defines a specific stage in the project. It happens when data are collected (when respondents are answering surveys). Fieldworks were traditionally done offline (Face to Face and Telephone) but progressively switched to digital methodologies such as mobile / online for the folowing reasons : better reach, speed, quality and price.
Questions that are defined to segment a certain part of the respondents. It is also used to direct respondents to a part of the survey, depending on their responses. An example could be a question about brand use, frequency of purchase...The answer to a filtering question will decide the further course of the interview - either the respondent passes to another section or the interview is closed.
Also see: Self completion questionnaire, Questionnaire
Qualitative method to gather individuals in a room. Usually, those participants are selected depending on their profile and are requested to participate in a group discussion. An incentive is given thanking for their time.
Also see: Online Focus Group