This is the type of question an interviewer will ask if he starts to doubt your ability to perform certain duties revolving around algorithm based development. Since software development at some level relies on algorithms and data structures, this will be an important question that you must understand and answer properly. If we look at how the binary search structure is broken down, it contains a binary search, or half-interval search which is a divide and conquer algorithm that seeks a position of an item in a sorted array. When a hiring manger asks about comparing inputs and output to the middle element of an array, they are asking if a search returns the position of an element. Since this is a feature important to Salesforce's Marketing Cloud, It's important to know and understand this concept. Another question that may be asked is whether or not an input is less than or greater than an element. If you have a sound understanding of these concepts, ask the interviewer to what level of detail you would like to answer their question. Some interviewers only want to hear a high level answer, and others want a detailed explanation.