What is meant by the term "discrete" number with respect to the imaginary part of the non-trivial zeros of $\zeta(s)$?

Question

The following link indicates the imaginary parts of the non-trivial zeros of the Riemann zeta function $\zeta(s)$ are "discrete" numbers.

New Insight into Proving the Riemann Hypothesis

What is meant by the term "discrete" number with respect to the imaginary part of the non-trivial zeros of $\zeta(s)$?

Answer 1

The meaning is that each of the zeros is isolated.