Some cameras can be plugged directly (via a cable that comes with the
camera) into a USB port, in which case the camera memory (with its image
files) is seen by explorer as a disk drive, and behaves as one. Other
cameras have removable memory cards and come with a small USB-cabled
card reader; these as far as explorer is concerned behave exactly as
above. In either case, the USB sees a removable storage device.
Digital cameras store their images as well-known common file types
(JPEGs, TIFFs, etc.) and that's how explorer handles them. Drag and drop
to the hard drive.
Spend a little time on the web looking at "digital camera review" sites.
This is hardly the forum for such basic (and off-topic) questions. You
need to know a lot more than you seem to about digicams if you're going
to invest in a good one.