BOOTCAMP is the partition, that gets created via Boot Camp Assistant to install Windows on your Mac.
Booting Windows on the Mac
The Devices section in Finder's Sidebar shows you the connected disks like internal HDDs or SSDs and its partitions. CDs and DVDs also show up there, as do external HDDs via USB or Firewire or eSATA or Thunderbolt. USB flash memory thumb drives also show up there.