When you shop on Amazon or any other E-commerce site, after adding items to your cart, usually you pay delivery fees to get them delivered to you right? Now, the gas fee is like a delivery fee, but this time, your items(read as transactions) aren't delivered to your doorstep, but to the recipient(if it’s a token) or the blockchain(if it’s a smart contract).

Gas fee is a fee paid to send a transaction on the blockchain. The cryptocurrency that gas fee is paid with is “ETH”, which is the Ethereum token.
Hence if you have Matic or Sol tokens, to send a transaction you will need Ether tokens to pay as gas fees.

Why Do We Pay Gas Fees?

There are many reasons why gas fees are necessary:

Executing transactions on the Blockchain requires computational power which costs gas.
To reduce malicious acts, and spamming the blockchain with unnecessary transactions. This puts a check on malicious actors, considering that they would have to spend ETH to send those transactions.
Transactions do not magically get on the Blockchain, they are people(known as validators) who add these transactions to the Blockchain and have to be paid for their hard work.

How is Gas Fee Calculated?

Like for most E-commerce sites, the more items purchased the higher the delivery fees; the same can be akin to the Blockchain. Gas fees do not have a fixed price, a combination of factors determines the price:

Network congestion: when many people are trying to send transactions at the same time, the price of gas will increase.
If it’s not an urgent transaction, you can wait it out until the traffic reduces.
Transaction type: the gas fee required to send an ERC-20 token is less than what is required to transfer an NFT. Therefore, the type of transaction determines the gas fees.

Gas fee is calculated by :

Unit of gas used * (base fee = priority fee)

Unit of gas by the computational power to process the transaction

Base fee: is set by the blockchain network
Priority fee: to make the node operators prioritize your transaction and include it in a block as soon as possible

Finally, one objective of the EIP4337(Account abstraction) proposal is reducing the hassle associated with paying gas fees that users encounter. The EIP proposes the use of Paymaster, which allows a blockchain network to pay the gas fee for users.

Many other improvements are in the works to improve the overall user experience when transacting on the Blockchain.