The use of optical/infrared interferometric methods by non-interferometric specialists is becoming more commonplace, and offers many opportunities for novel studies at high angular resolution. This paper presents an overview of current optical /IR interferometric methods for non-experts, with particular emphasis on the basic terminology and concepts. It also outlines the capabilities of current and planned interferometers, and reviews some recent science applications. The goal is to provide the background needed for a non-expert to assess the utility of interferometry for potential scientific studies, and to help identify those capabilities of existing arrays that offer the best prospects for future science exploitation.