ok, analouge is a wire, and digital is usally light. (somtimes high intensity wire)
Digital signals are not always optically transmitted; the difference between analog and digital , for audio, video, or data, is that analog is based on varying voltage, whereas digital is based on computer language (1s and 0s). My audio card, for example, has a digital o/p that is for a regular audio cable, but it spits out numbers, not waveforms. An optical cable, however, is more efficient.
I'm currently using an analog setup for my speakers, but the difference as far as that goes is just the amplifier . It'll either be able to convert that digital signal back into analog for the speakers, or it won't. Even if the speakers have a built-in digital processor and amp, to move those cones and get pretty sounds instead of modem-like squealing, the signal is analog when it actually gets to the speakers themselves. Naturally, if the source signal is digital, using an amp with digital capability will give you better fidelity, but in the end, the speakers themselves operate on a variable-voltage basis, because that's how your ears work.
