The notation \(\sum_{n=2}^{\infty} \binom{n}{2} z^{n}\) represents a power series where \(\binom{n}{2}\) is the binomial coefficient, defined as \(\frac{n!}{2!(n-2)!}\). This series starts at \(n=2\) and sums the terms involving \(z\) raised to the power of \(n\), multiplied by the binomial coefficient. The confusion arises from interpreting the brackets, which denote the binomial coefficient rather than a function. Understanding this notation is crucial for analyzing the series' behavior and convergence. The discussion emphasizes the importance of recognizing binomial coefficients in power series.