This is a data sheet for a PIR sensor. Your sensor should have a data sheet. Short of a part number there is no way for anyone here to guess what you have in front of you. Part number to data sheet is how it works. The output of the PIR in the link will be between 3.5 and 5 volts when it is active depending on the applied power depending on if it is set for active high or low. Assume active high.