When we read article on mining, we get a term "solving mathematical puzzle". To get a block, miner needs to solve the mathematical puzzle and whoever can solve the puzzle will be able to get a block and thus the reward (I can be wrong technically, this is what I know).
What's this puzzle all about? What do miner exactly solve? Please try to avoid technical term if possible, I would like to know in easy way.
I will try to keep this simple.
To understand the puzzle you will first have to understand how the SHA256 algorithm works.
Each block contains a merkle root, block header, block size, transactions, transaction count, nonce etc...
A miner uses his hashing power to generate hash of a block.
Example:
https://www.blockchain.com/btc/block/0000000000000000000ab0825fc30cf2844723262e0c0f2bfd048b2e752029daThe mathematical puzzle which the bitcoin miners solve are nothing but the hash with required number of leading zeroes.
The number of leading zeroes are determined based on the difficulty and when a miner finds out the hash it signals the other miners regarding the same thus claiming the block rewards.