The Internet has had a profound effect on everyone's lives, work, politics, and commerce--and increasingly, on the schools. Virtual schools have arrived, creating new opportunities for students, and also a set of challenges to the notions about schooling and the policies that govern public education. The potential application of technology in education may change the way that current versions of schools and schooling are limited in time and space. Will future technological innovations revamp educational conceptions of time, like class periods, grade levels, six-hour school days, and 180-day school years? These units of time, as well as physical school buildings, classrooms, and district boundaries, still define "school" for the vast majority of students. Will this change in the coming years? These are no longer unusual questions. Online and blended schools challenge some of the most basic assumptions about schooling. They no longer place groups of children of the same age in an assigned grade with a teacher and chalkboard in a room for 50-some minutes at a time in 180 six-hour days. With virtual schools, there has been a move to learning that is not bound by time, space, and pace, liberating education systems from the confines of rigid blocks of time and uninspired configurations of space to better meet the needs of students. While the potential for true educational transformation is great, one must begin by creating a shared understanding of what online and blended learning is, and how it is best implemented. This is the first in a series of briefs aimed at improving authorizer practices for virtual charter schools. This paper will define concepts in online learning, including full-time and blended learning, and will discuss recent trends in growth and governance of various types of online learning and virtual charter schools. (Contains 3 figures, 4 endnotes, and a glossary of key virtual school terms.)