Ethereum is a decentralised open-source blockchain system that features a powerful platform acting like a virtual world computer. 

Imagine a place where developers can create all kinds of cool applications, just like building houses or creating art in a virtual world. What makes Ethereum special is that it uses blockchain technology, which is like a digital ledger that keeps everything transparent and secure.

It’s like a global collaboration where people all around the world work together to solve puzzles. When they solve a puzzle, new information is added to the chain, forming a permanent record. To make things happen on this computer, people use Ether, the digital currency of Ethereum.