The discussion clarifies the use of variable notation in the Discrete-Time Fourier Transform (DTFT), specifically the distinction between capital omega (Ω) and e^(jω). Ω represents continuous frequency, which is suitable for the DTFT, while e^(jω) emphasizes the evaluation of frequency response on the unit circle. The z-transform is also mentioned as a crucial tool in digital signal processing (DSP), covering the entire complex plane. This notation helps in understanding the relationship between frequency and the DTFT. Overall, the choice of notation enhances clarity in analyzing frequency responses.