Modem is actually an odd acronym for Modulator-Demodulator. A modem takes a digital signal from your computer and converts to an analog signal so that it can be transferred through a phone line. This conversion is necessary because modems make use of regular phone lines which are analog. Newer technologies don't require this conversion, but more often than not, the term modem is still used. Since modems use phonelines, their transfer speeds are limited. The best modems can transmit data at approximately 56KB/s or maybe 112KB/s on a good day. That might seem like a lot except when you compare it to a typical corporate network or to broadband where speeds can easily reach 1000 KB/s.