What are the benefits and use cases of HVDC over HVAC (high voltage alternating current)?

I was reading https://www.energy.gov/oe/articles/connecting-country-hvdc to better understand how HVDC works in comparison to HVAC (high voltage alternating current).

My questions are thus:

1. How come HVDC retains more power across long distance transmission lines but DC loses more power?
2. Where is it feasible to use HVDC over AC / HVAC at the moment? For instance, in the article above, they mention undersea / submarine cables. Is it more efficient to use HVDC than HVAC / AC in those?
3. Other than the fact that you experience relatively less power loss with HVDC as opposed to AC / HVAC, what are the other advantages of HVDC? I understand HVDC can be used to connect separate AC networks for instance.