The sensors are one of the key elements in WP Admin Audit.
Think of them as little detectives, each of them trained to detect very specific events on your site.
You can decide which sensors to use or not to use. If a sensor is active and detects an event it will create an entry in the event log with relevant information and data.
For example the user login event will create an entry in the event log that – besides storing general information like the event date / time – records the name and email address of the user logging into the site.