Using cache vary with grouping operator

In the docs on caching, more specifically, vary by country

It states that

  • To create cache key variations based on one or more individual countries, use a pipe-delimited list. For example: Netlify-Vary: country=es|de

  • To group multiple countries together, use +. For example: Netlify-Vary: country=us|es+pt|dk+nl+de

What exaclty does the grouping operator do here?

I am confused because the docs say that You can specify individual countries or custom country groups. These are checked against a GeoIP lookup of the request IP address

In the second example I read it as *country equals us or spain and portugal or denmark and netherlands and germany.

This is correct. Is there a specific question about it?

The reason it confused me was because I apparently wrongly thought only one country was used in a request and it didn‘t make sense to me why an and operator would be present.

It’s not about per request. It’s more about saving different cache per country. So you could have cache saved differently for US, then another copy for Spain and Portugal and yet another copy for the next group.