At a single time multiple devices are connected trough a single network. Every device of the network can be accessed using an address named IP address which is unique for each device of a single network.
USB is one of the storage devices which are widely used. It is the most reliable device to transfer data from one computer to another. It can be easily carried in pocket because of its significant weightless size.
Many people use password to lock their computer because everyone has some data which can not be shared with others. Password is good to restrict access to computer but sometimes password is forgotten by owner of computer.