This is a new bootable 8GB flash drive used to clean install Mac OS X Mavericks 10.9.5 software on your Mac.
Clean Install Definition
To install an upgrade of an operating system (OS) on a hard drive that already has an OS running off of it without carrying over any settings of the older OS, such as user preferences or information about the hardware and/or the software.
Plug in the flash drive into a shutdown Mac.
Power on the Mac while holding the "Option" key.
Click on "OS X Base System".
Navigate to the drop down menu "Utilities" and select "Disk Utility".
In the top left column select your Mac's main hard drive and click on the "Erase" tab.
Select "Mac OS X (Extended)" in the drop down menu and click "Erase".
After it is finished formatting close out of Disk Utility.
Now click "Continue" and proceed with the onscreen directions to have your new clean installed operating system.
To install Mavericks, you need one of these Macs:
iMac (Mid-2007 or later)
MacBook (13-inch Aluminum, Late 2008), (13-inch, Early 2009 or later)
MacBook Pro (13-inch, Mid-2009 or later)
MacBook Pro (15-inch or 17-inch, Mid/Late 2007 or later)
MacBook Air (Late 2008 or later)
Mac Mini (Early 2009 or later)
Mac Pro (Early 2008 or later)
Xserve (Early 2009)
Your Mac also needs:
2 GB or more of memory
8 GB or more of available space