tl;dr: Sabbaticals are not an unpaid vacation but rather a chance to focus on longer-term scholarly projects.
Sabbaticals are an awesome feature of the academic job. I feel like they are often misunderstood by the world in general. This description is specifically about how sabbaticals work at the University of Waterloo; many North American universities are similar but not identical.
The normal distribution of work for tenure-track and tenured faculty members at the University of Waterloo is 40% teaching, 40% research, and 20% service. In my department, Electrical and Computer Engineering, 40% teaching means 3 one-semester courses per year: typically one term with 2 courses, one with 1 course, and one with no courses. For regular faculty members, service involves sitting on and chairing university committees (internal service), as well as participating in a research community by reviewing papers and being on committees (external service).
Temporary admin positions, like being Software Engineering Director, come with a negotiable change in distribution of work and teaching reduction. Mine was to 1 course in first year and 1.5 courses in subsequent years, with an extra .5 course teaching reduction for handling accreditation. Service was 50% of my workload during my SE Director term.
A normal sabbatical is at 85% pay. A faculty member can take a 1-year sabbatical after 6 years of service, or 6 months after 3 years. (The first 6-month sabbatical after one’s first 3 years of service is at 100% pay). During a sabbatical, the expectation is to have time to focus on research and external service, potentially doing longer-term visits to academic colleagues away from Waterloo. One is not expected to teach or do internal service during sabbatical.
What have I been doing on sabbatical?