What is UDL?
http://www.udlcenter.org/aboutudl/whatisudl
Universal design for learning (UDL) is a set of principles for designing curriculum that provides all individuals with equal opportunities to learn. Grounded in research of learner differences and effective instructional settings, UDL principles call for varied and flexible ways to:
  • Present or access information, concepts, and ideas (the "what" of learning),   
  • Plan and execute learning tasks (the "how" of learning), and
  • Get engaged--and stay engaged--in learning (the "why" of learning)

Why is UDL necessary? Students come to classrooms with a variety of skills, abilities, needs, interests, backgrounds, and learning styles. This diversity is confirmed by neuroscience: brain imaging technologies allow us to "see" the different ways learners respond to educational tasks and environments. Those differences can be as varied and unique as DNA or fingerprints.
Often curriculum--which includes the goals, methods, assessments, and materials we use to teach and learn--is "fixed" and inflexible. This turns individual differences into potential learning barriers as learners try to bend their individual styles, skills, and abilities to the curriculum's needs at the expense of genuine learning.
UDL turns this around: the curriculum is made flexible and customizable so that individuals can learn in ways that work best for them. A common aim of learning effectively and efficiently to high standards is achieved through many different means in the UDL curriculum.”