data packet 
While it may seem as though you send or receive a continuous stream of data every time you use the Internet, you don't. Instead, it's more efficient to break up the transmission into pieces called packets. These packets contain information about which computer sent the data and where the data is going. If a packet runs into a problem during its trip, it can attempt to find another route. When all the packets get where they're going, the recipient computer puts them together again. Modems generally send packets of around 64 characters along with some extras for error checking. When downloading files using a protocol such as Xmodem, however, the packets are larger. And when using Internet protocols such as TCP/IP, the packets are larger still--around 1,500 characters.