What are hit and false alarms, and how are they used in signal detection theory to seperate the experiment participants sensitivity to signals from the response bins of that participants?

Hits occur a signal is presented and the observer detects it. A false alarm occurs if no signal is presented and the observer detects it. The participant's sensitivity to the signals is usually computed by comparing hit rate with the false alarm rate, thus correcting for any bias the participant might bring to the testing situation.