Bitcoin's block reward halves every 210 000 blocks (210k * 10 minutes = 4 years), this block marks Bitcoin entering its 5th epoch with a block reward of 3.125 BTC down from its original of 50 BTC.
Interestingly there must have been a lot of people that wanted to get a transaction in the halving block, including fees and subsidy it resulted in a total reward of over 40 BTC for the pool that mined the block, ViaBTC.