[ntdev]What's the differenct about class co-installer and device co-installer?

Hello guys,

There has a dif code called DIF_INSTALLDEVICEFILES, according to msdn
It can handle class co-installer and class installer, but can’t handle
device co-installer.

I have been confused with class co-instlaler and device co-installer. Can
you give me some instruction about them?
What’s the difference about them?

Thanks in advance!