Aspect	Amplifier	Repeater
Signal type	Boosts analog signals	Regenerates digital signals
Method	Increases the amplitude/strength of the entire incoming waveform, including any noise picked up along the way	Detects the original bit pattern and reconstructs a clean, fresh digital signal, discarding accumulated noise
Noise handling	Noise is amplified along with the signal — degrades over multiple hops	Noise does not accumulate — each hop starts fresh
Layer	Physical layer, used in analog transmission (e.g. old telephone lines)	Physical layer, used in digital transmission (e.g. Ethernet, digital telecom)
Typical use	Long-distance analog communication links	LANs and digital transmission lines

In short: an amplifier blindly strengthens whatever signal (and noise) arrives, while a repeater reads the digital data and retransmits a clean copy — making repeaters more reliable for digital networks over long distances.