So this is a 2-year-old block, and ~$15 million (just estimating at ~500/btc) being shifted around in that set isn't abormal? (Not sure how recycling of big amounts works, I'm not being facetious)
Block is just a set of transactions. New block happens every 10 minutes and contains all the transactions that all the bitcoin users sent during that period.
So, this one transaction is interesting because it involves an old address. Other transactions in this block are probably unrelated.
