Contact is the visible baseline
A contact mine is triggered by physical contact with a vessel. It is the easiest concept to picture, but it is only one part of mine warfare’s technical history.
Magnetic and acoustic signatures
Magnetic and acoustic mines respond to characteristics associated with a passing vessel. That helps explain why materials, electrical systems, noise and operating procedure entered the design conversation.
Do not make the category do too much
The broad type is a starting point, not a complete technical specification. A reader researching a particular period should follow the official history and record series for that conflict or theater.
Source note. This page separates documented history, archival observation and editorial explanation. Where a source does not establish a detail, the detail is left open.