Application development is a broad set of technologies, and it can apply to building applications using tools from several software brands. There are typically two categories of technologies within application development. The first is client-side scripting/coding using technologies such as HTML, JavaScript, jQuery, etc. The second is Server side scripting/coding using technologies such as PHP, ASP (Microsoft), Cold Fusion, Python, etc. The reason a hiring manager at NTT DATA would ask this question is to see which category you fall under. They want to know if you're qualified to do both. Most consultants who have spent considerable time consulting on application development projects should have a solid working knowledge of both. The hiring manager might also ask about the application development lifecycle which is now more geared toward web application development. Almost all applications nowadays will be developed for the web. When you answer these questions, make sure you understand what they are asking before giving a full explanation.