Quality Assurance are the steps which are taken to ensure the product which is to be made has desired properties. it is kind of the guidelines, specifications and plans.
Quality control are the steps which are taken to ensure the intended properties inherit in the product during manufacturing process by applying detection methodology like inspections, check sheets, NCR etc.
QA can be termed as actions lead to prevention before its occurrence.
QC can be termed as actions for detection's of deviation.
Though they look different from each other but they are both sides of single coin.
You detect something, you will create a mechanism for its prevention.
The detection can be done either by doing practical or by doing critical thinking on phases of process.