Is "GHz" a Measure of Capacity, Frequency or Clock Speed? Yes.

Bandwidth (capacity) discussions sometimes get confused because we use some terms in different ways. Consider the ways we use “Hertz.” We talk about signal frequencies as a way of describing different blocks of capacity at different wavelengths (optical or radio frequency).

source: Simplifying Theory

Think of this usage as musical notes, which can range from low to high in multiple octaves. So mobile signals can use spectrum at lower (600 MHz, 800 MHz), mid-range (2 GHz) or high frequencies (30 GHz to 100 GHz)

We also use the same terms to describe channel sizes, which relate to potential data rates.

source: Bitfeed

Personal computer makers use similar terms to describe processing speed (clock speed).

Then we use related terms such as “megabits per second” (Mbps) to describe throughput and “megabytes” as a measure of capacity or throughput as well.

Here’s a tutorial on such things, at least in the areas of signal frequencies and channel bandwidth.