Mining blocks and Rewards

Blockchain consists of blocks. Any miner node can create, or as they say, "mine" blocks. To do this, he must collect several pending (not included in other blocks) transactions in a new block and select a code so that the hash of the whole block (together with this code) matches certain network rules.
It is impossible to calculate this code. Therefore, the node simply goes through all the possible variants. These rules (complexity) of the network can change and, accordingly, the time spent by iterate the code will also change.
Having created the block by all the rules, the node notifies the other nodes about it. The nodes verify the correctness of the block and adds its to chain. Thus, the chain grows, and transactions that included into the block are confirmed. The number of confirmations is the number of blocks, located after the block in which the transaction is added, minus 1.

For each block mined, the miner receives a reward. The reward is received only by the first to get the block.