As far as I understood, it is basically a process through which blocks (that contains information about transactions) are verified.
Not quite. Every node in the system, not just a mining node, can verify a bock. To verify a block is not computationally expensive. However, mining is needed for creation of
new blocks, to extend the blockchain.
For that miners has to perform simple calculations Nodes (Computers) does that for miners. The one who performs it the first gets the reward .
Each individual calculation is indeed relatively simple, but it takes an incredibly huge number of them to find the right solution. The miner who finds it first, gets the right to write the new block and collect the reward.