What is a 2 channel amplifier?

Answer 1

A 2 channel aplifier is an amplifier that can operate two channels. It is basically two 1-channel amplifiers in a single box. This unit is usually intended for operating a left speaker and a right speaker.

A channel is the signal/power combination intended for one specific speaker. A 'Stereo' audio system typically has a left channel and a right channel. More advanced audio systems may have separate channels for different types of speakers (midrange, woofer, tweeter, very commonly subwoofer, sometimes supertweeter) or for rear channels (surround.) This sort of setup was modern during the early 90s.

A bridged 2 channel amplifier is constructed in such a way that the amplifiers can be set up to operate inline providing the effect of a more powerful one-channel amplifier. If durability is a concern, a bridgeable two channel amplifier used for two channels tends to work well because it's likely to have higher quality or just more diodes so as not to be destroyed too quickly during bridged operation. Using a more powerful amplifier with the gain turned down is also a good idea if longevity is a concern.