What does radiopharmaceutical uptake from a bone scan mean in layman's terms?

Tracer uptake: Read the report. But it sounds like it means that there is increased bone metabolism at that location. The radiopharmaceutical maps calcium activity (osteoblastic) of the bone. Can have increased metabolism in response to mechanical stress, a fracture, cancer, infection, and miscellaneous reasons.

Bone metabolism: Bone scan involves intravenous injection of radiotracer usually technetium 99m mdp which accumulates in skeleton. Scan may involve early phase(5-10 min) and late phase(2-3 hr) imaging. Increased uptake is seen in fractures, tumors, infection, etc. Decreased uptake is seen in metal artifacts, aggressive tumor/infection, & loss of blood supply to bones. Bone scan very sensitive but not specific.