We define QC as - simply the observational techniques and activities used to verify that requirements have been fulfilled.
For us it’s a regulatory process that gathers measurements, compares those measurements to a standard, and determines whether or not the requirements for quality have been met. This data acquisition and analysis also facilitates quality improvements.
When requirements are met the product or service moves forward to the next step in the process. When requirements are not met, the material or service is identified as nonconforming and appropriate action is taken, usually rework.
Simply put, Quality Control (QC) is Inspection. Its emphasis is to uncover defects and report them.
Alternatively, Quality Assurance (QA) attempts to improve and stabilize processes to avoid defects in the first place.
QA is before and QC is after! Applying QC is intended to prevent defect escapes to the customer either internal or external.