Hi,
currently, the mining reward is 12,5 BTC for each block mined.
But that won't be always the case. In approximatively 685 days, Bitcoin block reward will be halved, which means miners will only be rewarded with 6,25 BTC afterwards.
Reward is halved every 210,000 blocks.
If you want to know more about reward halving, you can go there:
https://www.bitcoinblockhalf.com/and here:
https://blockonomi.com/bitcoin-halving/Indeed, at first the reward which miners get at first are more than 12.5 btc. About reward halving after miners mined 210,000 blocks is called halving.