The term modem comes from the two words modulator-demodulator. It s a device that ensures the phone line is able to transmit and receive computer data. External modems are slightly more expensive, probably only because they enable the user to see what s going on. Those combinations of eight flashing lights mean data is trying to reach the computer screen. Although there are other ways of understanding what is going on it s not so easy to detect this with an internal modem.
Externals are easier to attach, too.
They re far more common and popular than internals. When you buy a PC check whether it comes with an in-built modem or not. The slowest modems around these days are 14,400bps - but that is extremely slow. In fact very early ones were much slower than this and are today only museum items. Other commonly purchased types of modem currently available are those with speeds of 28,800bps and 33,600bps.