Garbage:
1) From a user's perceptual point-of-view, garbage is often used to mean anything on your display screen that looks unreadable or unviewable.
2) From a programming point-of-view, garbage is data that has been placed in random access memory space obtained from the operating system that is no longer needed. Freeing the space for reuse is called "garbage collecting."
Gateway
A gateway is a network point that acts as an entrance to another network. On the Internet, a node or stopping point can be either a gateway node or a host (end-point) node. Both the computers of Internet users and the computers that serve pages to users are host nodes. The computers that control traffic within your company's network or at your local Internet service provider (ISP) are gateway nodes.
Ghost is a software product from Symantec that can clone (copy) the entire contents of a hard disk to another computer's hard disk or to storage media, automatically formatting and partitioning the target disk. This product is especially useful where one system is to be replicated on a number of computers or when someone wants to back up everything on their personal computer.
Ghost imaging is the copying of the contents of a computer's hard disk into a single compressed file or set of files (referred to as an image) so that the contents of the hard disk, including configuration information and applications, can be copied to the hard disk of other computers or onto an optical disc for temporary storage.