In 1998, two groups presented startling evidence that the expansion of the universe is accelerating, and the term "dark energy" was coined as a label for the cause of the acceleration. What is the nature of this mysterious component that we now believe makes up more than 70 percent of the energy density of the universe? What types of evidence for dark energy are there, and how solid is it? What techniques will yield better answers? What are the next steps? These are a few of the questions that have captured the attention of cosmologists as well as the general public. This talk will attempt to explain the questions and a few of the answers.