The difference between width
and device-width
can be a bit unclear. I'll try to explain.
device-width
refers to the width of the device itself, in other words, the screen resolution of the device. Lets say your screen's resolution is 1280x800. This means the screen is 1280 pixels across, so it has a device-width
of 1280 pixels.
In contrast, width
refers to the width of your browser's viewport size.
In most cases width
is more versatile when it comes to creating responsive webpages (and it is the method I would recommend you'd use), though device-width
could be useful when you wish to specifically target mobile devices (and not desktops with a very small browser window).