on-demand vs on-access

edited January 2018 in General

Hey there,

I'm going to whitelist my usb flash drive since BItDefender starts scanning it every day after boot-up and it takes more than a hour to complete (8 GB usb 2.0), beside the assumption that this might not be that healthy for the usb drive...

By whitelisting it, there comes a dialog asking me if excluding it from "on-demand scanning", "on-access scanning" or both. What is the difference?

I can guess that "on-access" is obviously meaning that when I access it. But "on-demand"? When I have a demand of my USB drive then I will access it soon either way... :P 

Can't find an answer in online help or forum.

Thanks in advance!

PS: One search request per minute for registred users in forum? okay...