This chapter reviews a range of research that illuminates what is actually happening when someone reads. Reading is a skill that takes decades to master, and is strongly influenced by the context in which it occurs. While, like riding a bicycle, reading is a skill we can take for granted once mastered, in fact the picture underneath is highly complex. The complexity of reading is suggested by the effort that is expended by us all to learn how to master it. A better understanding of what is happening when we read, and how we are affected by our interactions during reading, will help us appreciate why specific techniques are effective (or not), and help us design and plan better interactions.