Block reference

A block reference (often shortened to just "block" in conversation) is one placement of a block definition in a drawing, at a given position, rotation and scale. A single definition might have hundreds of references scattered across a drawing set — each one is a separate object with its own handle and its own attribute values, even though they all share the same underlying geometry.

This is the key distinction the site's own docs keep coming back to: editing a block reference's attribute values (its data) is a different operation from editing the block definition itself (its geometry/template) — and different tools exist for each.