Ask HN: Best online resources to learn about Bitcoin/Cryptocurrency?

Over this Thanksgiving holiday weekend, I wanted to provide my Dad (a retired banker) with some online links to learn about Bitcoin and cryptocurrency.

I, myself, don't know much about Bitcoin nor cryptocurrency, so I would like to read the material, too.

Where would someone start - what are good online resources that give a good introductory explanation of what it is, as well as the deeper details of it, if, say, someone was thinking about making a sizable investment in it and wanted to have a thorough understanding of it all?

It always seems to me there's a lot of people on HN that are quite knowledgeable about this stuff, so I just thought I'd ask here.

Thanks and Happy Thanksgiving to you all.