Psutil module in python

what does interval parameter in psutil module stand for explain clearly i have read many websites but still not able to understand

if you want to know the CPU usage during a specific call , you have to either
(a) call it before and after the function,
or (b) call it from another thread or process running in parallel with the call, and for the same time as the call by passing an interval .

Psutil in Python, is a library, used to know about the system details and how various resources like CPU, sensors etc., are used in the system.

To install this library type in this command in linux ubuntu:
sudo pip install psutil

Of all the functions available in this library, interval is a parameter of function,

psutil.cpu_percent (interval=None, percpu=False) - Returns a float representing the current system-wide CPU utilization as a percentage.

interval - the time duration parameter over which the average CPU usage is calculated.
percpu - if True, returns a list of floats representing the utilization as a percentage for each CPU.