A ledger is a principal book having all the information of economic transactions like debit, credit etc
In the bitcoin network ledger is distributed among every participant or nodes (cryptocurrencies are decentralized), so everyone who is connected to the network has a copy of that ledger on their computer.
Miner’s main role is to add information related to the transaction in the ledger and form a block. Before making that particular miner validate that information and bind it to the block and send that block to the network. Everyone on the network has that block of the transaction on their ledger.
Block created by the miner then linked to rest of the block present on the network and finally make blockchain. For doing this miner have been awarded bitcoin (in case of bitcoin mining). Someone called this process mining which is very similar to mining of gold like a gold miner mines gold bitcoin miner mines bitcoin.
As bitcoin miners approve Bitcoin transactions so definitely more miners mean more secure transactions and network. Initially, miners use CPU (central processing unit) to solve the complex mathematical problems to mine bitcoin now it is replaced by GPU (graphics processing unit) to solve the problems graphics cards which was developed for gaming mines faster than CPU. But GPU consumes more electricity and produce more heat.
ASIC Application Specific Integrated Circuit Chips are designed specifically for bitcoin mining.It mines faster and even consumes less electricity. As the mining process becomes popular more people started ming and makes complicated for individuals to solve the problem so to overcome these miners developed a tool called POOL MINING.
Many miners combine together to mine, and each miner awarded proportionately the number of bitcoins mined. This method even works faster than GPU.
Mining is an integral part of cryptocurrency word as it ensures stability, safety, and security of the network.