A design with low fidelity leaves out details so you can test a basic idea quickly. It might use a sketch, simple blocks or a short click-through flow. The goal is to answer a structural question before refining the visuals.
Test a specific question
For a reference page, ask whether the definition, example and related lesson appear in a useful order. Sketch two arrangements using real section names. Ask someone to find the example and explain what they expect the next link to do.
Keep enough realism
A rough prototype still needs recognizable content and actions. If every label says “placeholder,” people cannot judge whether the navigation makes sense. Avoid adding color and decoration simply to make it look finished.
Know what the test cannot tell you
A paper sketch cannot verify keyboard focus or responsive CSS. A click-through image cannot establish real form validation. Move to a detailed prototype or working HTML when those become the questions.
Exercise: sketch a lesson with three sections, then rearrange it after watching one person find a specific answer. Record the observation separately from your interpretation. A rough prototype can be easier to change, but it does not guarantee faster delivery or better decisions.
See wireframes for layout planning and usability testing for how to observe a task.
Sources
Reference 1 provide the technical details and current compatibility information.