PAM4 signaling is a type of data transmission technique that uses four distinct signal levels to represent information. This allows for the encoding of two bits of data per symbol, effectively doubling the amount of information transmitted compared to traditional NRZ (Non-Return-to-Zero) signaling, which only uses two levels. By utilizing PAM4, communication systems can achieve higher data rates over the same bandwidth, making it particularly useful in high-speed applications like data centers and telecommunications. However, PAM4 signaling can be more susceptible to noise and distortion, requiring advanced error correction techniques to maintain data integrity.