MVC stands for model view controller. MVCs typically organize webapps into a well-structured pattern, making code easier to maintain. The term is well-known by developers and some famous examples of MVCs include backbone.js and angular.js. What makes this question interesting is not whether the frontend interviewee has used an MVC, but what his or her preferences and experience reveal. Candidates who are able to articulate why they use one MVC over another show that they are engaged in what they do, care about the technology and have considered different options. You want to be able to trust your frontend developer to keep up to date with which technologies are relevant and have a clear idea of when and what should be used.