Confused by using quotation marks for <= and >= and using & in countifs function

As far as I remember we used quotation marks and & for text data, how are they being used here for comparison between data points? What's wrong with the following code?
=COUNTIFS($B$13:$B$32,>=$E15,$B$13:$B$32,<=$F15)

I really appreciate it if you help me out!