Surveillance techniques refer to methods used to monitor individuals or groups to gather information. These techniques can include physical observation, where a person is watched in real-time, and electronic monitoring, which involves using devices like cameras or microphones. Surveillance can be employed for various purposes, such as security, law enforcement, or research. Another common technique is data surveillance, which involves collecting and analyzing digital information from sources like social media or online transactions. This method helps organizations understand behavior patterns and trends. Overall, surveillance techniques play a significant role in ensuring safety and gathering intelligence in various fields.