Yes there is, and it's not that different from reddit. The sorting algorithm is what they refer to. Eg, hot is some balance of time vs votes, which greatly favours newer posts (too new, IMO -- posts it shows will typically no comments or maybe just one or two). Active favours high commenting rates and based on my observations, it seems to drop off around 2 days (too old, IMO -- a considerable number of posts shown by this algorithm seem to be around the 2 day mark). The top and new algorithms are straightforward enough.

All the algorithms favour big communities. There's a "best" algorithm in development, which would try to look at the top for each community and thus give smaller communities a chance. I can't wait for that, because right now, you'll rarely if ever see a small community hit the front page and it sucks bad.