If you've ever installed or used a fresh Wordpress site, you'll be familiar with the default "Twenty [Year]" theme which comes with every Wordpress site. It's the flagship theme and is made to be customised as much as possible for anyone and everyone.
Automattic, the people behind Wordpress have realised that Wordpress is being used more as a content management system than a traditional blog, because it's so versatile. With it being open source, people can adapt Wordpress and make it to be whatever they like.
The new Twenty Twelve theme takes this into account and makes the homepage more of a "welcome" page, rather than a list of blog posts as before. You can now add a short welcome paragraph, some images, videos and whatever else you'd like. Of course everything is organised by widgets, so your homepage won't end up looking like everyone else who's using the same theme.
The theme is fully responsive so it works brilliantly on phones and tablets. Some people are still a bit weary with responsive, myself included, because I feel like responsive design only works with certain types of sites. I might change my mind in a few months though and think responsive design is the way forward.
The new theme uses a new free Google font, Open Sans. It's a brilliant font and one which I've been using in my web design projects lately. Forget Arial and Helvetica.