>>7725285 (OP)
Copying and reference are similar and share things in common but the goal, process, mental state and outcome are different.
When copying, you want to understand how/why something looks that way. There are many different ways of copying (pic related). You might have the goal of copying it as accurately as possible (reproduction), to train your observational and accuracy skills. Or you can analyze it and break it down using construction drawing. Or be more 2D shaped focused like anime style. If you're copying an illustration, you can ask, Why did the artist use this kind of line here, what kind of form is this, why is there a hard shadow here etc. Hopefully this expands your visual library, improves your skills and knowledge.
When using a reference for an illustration, the goal is to accurately portray something in your original artwork. You select a specific pose, anatomical feature, texture, color palette etc. to use as reference and integrate it into your piece. You could use a photo of lizard to help inform your drawing of a dragon. The result is hopefully more believable, accurate, or visually appealing etc.
Most of /ic/ gets stuck studying too much and not making enough finished pieces. Polishing a turd is bad but never even trying will mean you get stuck in just studying and never apply what you learn. Applying what you learn to pieces you care about is when you really progress.