Digital is a trait of data (and of signals) which represent information as a sequence of 0s and 1s.
Digital data often represents qualitative variables. For example, each of the 26 letters in the English alphabet (and of many alphabets) is digitally represented via the Unicode standard. Digital data also often represents dimensional variables. For example, analog signals are often represented as digital data.
Digital data is never identical to analog data. However, the information loss (and the resulting significance of abstraction) of digital data can be practically eliminated by encoding with sufficient bit depth. Digital data isn't subject to the predictable and inevitable degradation which analog data experiences when repeatedly replicated, transmitted or processed, so digital data is a fundamental element of most large signaling and computing networks.