Signal Integrity (SI) refers to preserving the quality of data transmitted through a channel, ensuring that the digital sequence of ones and zeros can be accurately recovered from the analog signal. The primary tool for assessing SI is the eye diagram, which is created on an oscilloscope by displaying many random bits. Key factors affecting SI include jitter, signal loss, and noise, which can arise from issues like crosstalk (interference between channels) and inter-symbol interference (interference between consecutive bits).