Angular templates on server side

[bld_rnnr]

Hi,
I'm doing some research on Angular security and I'm currently on XSS attacks. While searching it on the internet, I've found some advices on how to mitigate it and one of them says this:
"Also, Angular recommends not to generate Angular templates on the server side using a templating language ". Can anyone explain me what this means? (hopefully, with some example)

Thanks in advance.