It is a concept used within the Ethereum network as a stable unit of measure for network charges. It allows measuring the cost of the work required to execute actions independently of the price of Ether (ETH). Using this unit of measure is more practical for a virtual machine-based system where the use of smart contracts is very popular. In addition to allowing you to protect the network from potential denial of service (DDoS) attacks.
To better illustrate, one of the aspects in which Bitcoin and Ethereum differ is the way in which the ability of the system to process transactions is measured and/or limited. While in the Bitcoin (BTC) network there is a limit to the maximum size of the blocks of 1 MB –in the Bitcoin Cash (BCH) network it would be 32 MB–, in the Ethereum (ETH) network this limit is expressed in a specific amount of “gas” (currently about 8,200,000 gas) that can fluctuate depending on the miners.
No, the only digital currency native to the Ethereum network is Ether, “Gas” is a concept or unit of measurement to know the value of a process within this network.
Actually, these two functionalities have a symbiotic relationship in terms of value, since in order to carry out any operation within the Ethereum network, a certain amount of Gas is required and this is represented in Ethers, therefore both are important, however, Ether has a greater use value than gas, that is, it can be used for many things.
The word “Gas” refers to an allegory of the system’s fuel, since to run a vehicle up to a certain distance, a specific amount of fuel is required, and this is precisely what Gas does within the Ethereum system.