How do words mean? What is the nature of meaning? How can we grasp a word's meaning? The frame-semantic approach developed in this book offers some well-founded answers to such long-standing, but still controversial issues. Following Charles Fillmore's definition of frames as both organizers of experience and tools for understanding, the monograph attempts to examine one of the most important concepts of Cognitive Linguistics in more detail. The point of departure is Fillmore's conception of "frames of understanding" - an approach to (cognitive) semantics that Fillmore developed from 1975 to 1985. The envisaged Understanding Semantics ("U-Semantics") is a semantic theory sui generis whose significance for linguistic research cannot be overestimated. In addition to its crucial role in the development of the theoretical foundations of U-semantics, corpus-based frame semantics can be applied fruitfully in the investigation of knowledge-building processes in text and discourse.