This document discusses theories that can be applied to online course design, including Zone of Proximal Development, Bloom's Taxonomy, and scaffolding. It explains that Zone of Proximal Development refers to the difference between what students can do independently and with assistance. Bloom's Taxonomy organizes learning objectives from lower to higher order thinking skills. Scaffolding provides support to help students achieve learning objectives. The document provides examples of how to incorporate these theories when designing online course content, tools, and assessments to effectively support students' learning.