A "128-bit" system refers to the width of data that a computer's processor can handle at one time. This means it can process 128 bits of information simultaneously, allowing for more complex calculations and larger data sets compared to smaller bit systems, like 32-bit or 64-bit. In terms of memory addressing, a 128-bit architecture can theoretically access a vast amount of memory, significantly more than what is possible with lower bit systems. This capability is particularly useful in applications requiring high performance, such as cryptography, data processing, and high-performance computing.