Bi-wiring: skip it. Passive bi-amping from spare AVR channels: try it, it is free. Full active bi-amping: another world, not a weekend job.
Both use the split terminals on the back of many speakers, the two pairs of binding posts joined by a metal strap. The strap comes off, and what you connect after that decides which of the two you are doing.
Bi-wiring runs two cable pairs from the same amplifier output to the speaker's separated bass and treble sections. The claim is that keeping the currents apart improves clarity. Plausible on paper? Just about. Measurable? Barely, and the case for anything audible is thin. We would never put money there ahead of anything else in the chain. If a shop is selling you a second run of expensive cable for this, that money belongs in the speakers.
Bi-amping dedicates separate amplifier channels to each section. The passive version, using an AVR's idle channels (many AVRs offer front bi-amp as an assignable mode; check your manual before wiring anything), is a free experiment. Each section gets its own channel's current, and with hungry speakers in a large room the gain can be modest but real, chiefly in bass control at volume. Modest is the key word. Nobody has bi-amped a speaker into a different speaker.
Full active bi-amping is different: an electronic crossover before the amplifiers, one amplifier channel per driver, the speaker's passive crossover removed. Studio and enthusiast builds live there, and it needs measurement to set up. Not something to try because a forum said so.
Practical guidance. Idle AVR channels, speakers with dual terminals, and a spare cable run? Try passive bi-amping, judge with your own ears over a week, and keep it if it earns its place. Buying anything specifically to bi-wire? Redirect that money to the speakers or the room; either will be audible from the first evening.
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