Ethereum is a decentralized computing platform based on blockchain technology. It was originally launched as a platform for creating smart contracts and dApps. These are programs designed to automate some part of their interactions with other parties. It allows users to create new programs called "smart contracts," which can be written by anyone, even those not familiar with coding.
In this way, the program is self-executing, meaning it will automatically perform the functions specified when triggered by certain events. Once the contract is ready, it will need to be deployed on the Ethereum network.
When it gets deployed, the developers will have to pay a gas fee through Ether (ETH). This ETH token is the currency for the whole ecosystem and is required to pay transaction fees. Every time someone uses the contract, they will pay a gas fee for the Ethereum blockchain to confirm the transaction.
A smart contract is basically the code logic behind Dapps (decentralized applications). Dapps are applications that exist entirely within the blockchain. Instead of using a centralized server, each Dapp runs on the decentralized Ethereum network. This means that all the data stored on the app is encrypted, and there is no central point of failure.
In summary, Ethereum is a platform for building decentralized applications (Dapps) and creating smart contracts. Read also our centralized vs decentralized
article to understand why having applications on decentralized blockchain is very important for the future of our tech world.