Quality Control is often abreviated as QC
Quality Control is defined as "the part of quality management focused on fulfilling quality requirements." Quality Control is one small part of quality assurance. Quality control is usually thought of in terms of inspection and testing, whereas quality assurance systems are all the things that go into producing quality goods or services that meet the customer's requirements, and provide the organization with whatever it's motivations are (profit?)
Another definition of quality control descibes it as "the process relating to gathering process data and analyzing the data to determine whether the process exhibits nonrandom variation." Quality Control often referrs to Inspection of finished products, meaning to check whether they meet the desired Requirements and Specifications. But it is not limited to inspecting products as it might also include detecting the cause for non-conformities and not meeting the requirements documented in the specifications for the product.
In all production processes, the extent to which products meet quality specifications must be monitored. In the most general terms, there are two "enemies" of product quality: (1) deviations from target specifications, and (2) excessive variability around target specifications. During the earlier stages of developing the production process, designed experiments are often used to optimize these two quality characteristics.
The general approach to on-line quality control is straightforward: We simply extract samples of a certain size from the ongoing production process. We then produce line charts of the variability in those samples, and consider their closeness to target specifications. If a trend emerges in those lines, or if samples fall outside pre-specified limits, then we declare the process to be out of control and take action to find the cause of the problem. These types of charts are sometimes also referred to as Shewhart control charts (named after W. A. Shewhart who is generally credited as being the first to introduce these methods; see Shewhart, 1931). Those control charts are often referred to as "Quality Control Chart" or Statistical Process Control Chart (SPC-Chart). Part of "the seven basic tools of Quality".