The home page has a complicated algorithm that seems to take many variables into account to determine the 'hottest' / 'best new' stories (including measures to punish cheating etc.).
As far as I can see the 'best' page seems to simply take all articles submitted in the past ~3 days or so, sort them according to the number of points, and show the top 30 in that order.
Of course, the 'best' page works only thanks to the upvotes articles get (mainly) on the home page.
Time degrades points more slowly on /best, so it will usually show the top stories from the past 3(ish) days rather than the past 12-24 hours. Perfect for when you've been away for a few days and looking to invest some time in reading.
As far as I can see the 'best' page seems to simply take all articles submitted in the past ~3 days or so, sort them according to the number of points, and show the top 30 in that order.
Of course, the 'best' page works only thanks to the upvotes articles get (mainly) on the home page.