This document presents a framework for understanding the dimensions of personalization in technology-enhanced learning (TEL). The framework identifies six key dimensions: 1) what is being personalized, 2) the type of learning, 3) personal learner characteristics, 4) who or what is doing the personalization, 5) how personalization is carried out, and 6) the impact and beneficiaries. The framework was developed through analyzing literature on personalization in TEL. Examples of how the dimensions apply to intelligent tutoring systems and learning analytics are provided. The framework is intended to provide a common language for discussing personalization and guide its design and implementation in TEL environments.