How does 'alt-right' differ from 'extremist-right'? Is 'alt-right' just a euphemism?

The term ‘alt-right’ seems to have been coined to draw a distinction from the traditional right wing.

But ‘alt’, at least to me, seems more like a PR euphemism than a true description.

In terms of ideology or belief, how does alt-right differ from extreme right or even far right?

Are we seeing the Trump Taliban?