What is a corrupted hard drive and how can I recover data from it?

What is a corrupted hard drive and what are the symptoms?

Data corruption is a state where the data within a file or storage device is altered from its original state, causing it to behave differently or become completely inaccessible.

Common symptoms of hard drive corruption include:

• The drive is completely inaccessible
• Sluggish performance
• Missing files
• "Blue screen of death" (BSoD)