Using the Google Fonts site

Use the font’s details page to learn more about its static fonts.

To investigate a variable Google font, go to the Google Fonts
website. Note that in the upper right corner of each font card,
it says either variable for a variable font, or
x styles indicating how many styles a static
font supports.

Make sure that Show only variable fonts is not checked
and the search field is empty.

Open the Font properties menu. Check the Number of styles
checkbox, and move the slider to 10+.

Select a font, such as Roboto to open up its details page.

Roboto has 12 styles, and each style is previewed on its details
page, along with the name of that variation.

In real time, move the pixel slider to preview the font at
different pixel sizes.

Select the Type tester tab to see the supported styles for
the font. In this case, there are 3 supported styles.