The objective of a technical writer is to help the users in using the product. When a user is struck in understanding a feature or task, they consults the document as a reference. While an instructional designer make the user learn. The learner needs to go through the complete instructional design deliverable. If we talk about WBTs or CBTs, each and every activity of learner is tracked. The learner uses the instructional design deliverable as a textbook and not as a reference guide.
To conclude, technical writers write documents for potential users while instructional designers for potential learners.
