Personally identifiable information (PII) is information that identifies, links, relates to or describes a person, such as phone numbers, medical information or biometric data. Devices, websites and networks can collect data people do not notice, and hidden collection can raise privacy concerns. Scattered bits of personal data can be combined to learn about one person, and information put online is hard to delete. The crew asks first, collects only what its question needs, uses IDs instead of names and plans to share totals, not rows.