This document discusses variability management in software product lines. It begins by defining a software product line as a set of products that share a common architecture and reusable components. Variability management involves explicitly representing variability throughout the lifecycle, managing dependencies between variabilities, and supporting instantiations of variabilities. It is a key activity for software product line success as it requires systematically identifying and managing variabilities to support reuse-based development. The document outlines approaches to variability management and compares issues in the area.