The type of file that would be MOST likely to be measured in kilobytes is an email message. Email messages typically contain text and possibly some small attachments, which usually result in a file size that can be in the kilobyte range.
In contrast, a 60-minute video and a 3-minute song file would typically be measured in megabytes or even gigabytes, and a company's database would likely be much larger than kilobytes as well.