Every block begins with a coinbase transaction. It spends no earlier output; it creates new bitcoin up to the block subsidy plus the fees of the block's other transactions, paid to whatever outputs the miner chose. A coinbase that pays out more than that makes the block invalid.
Its input field is free space the miner fills in. Since BIP 34 it must begin with the block's height; pools usually add a tag naming themselves, which, with payout addresses, is where explorers' pool labels come from. Since SegWit, a block with witness data also commits to it in a coinbase output.
Because its outputs are the miner's whole reward, fee revenue can be read from it: coinbase outputs minus the subsidy for that height, which counts only what the miner actually claimed.