there is no F/B involved the emitter simply follows the changes
on its base.
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With a common emitter amplifier it's the emitter that is usually
grounded.
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A: When a signal is not amplified but simply taken from an
emitter the reason is that the emitter will provide better current
capabilities
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Depending on context, it could be an infra-red emitter. An
emitter that emits at a wavelength longer than that of visible
red.
infra red emitter is a special pn juction device in which
emitter region emits infrared rays
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I think you mean a common emitter amplifier, which is an amplifier of voltage. Emitter-follower or common collector amplifiers are used to match impedances, or to amplify power or current. The emitter-follower is a type of common emitter circuit that has a resistor between the emitter and ground. The output signal is taken from the point between the emitter and its resistor.