What is virus scanning and how does it work?

What will be an ideal response?

Virus scanning refers to the process of examining files or e-mail messages for filenames, file
extensions such as .exe (for executable code) or .zip (for zipped files), and other indications
that viruses are present. Many viruses have suspicious file extensions, but some seem innocuous.
Antivirus software uses several methods to look for malware, including comparisons to
the software's current signature files, which contain a pattern of known viruses. Signature
files are the primary reason for keeping your antivirus software updated; antivirus software
vendors frequently create updates and make them available for customers to download.
When antivirus software recognizes the presence of viruses, it deletes them from the file system or places them in a storage area called a quarantine where they cannot replicate themselves or do harm to other files.