They are used for demo purposes only. they interact with the contract on the blockchain.
They only work on ethereum testnet such as Ropsten, Kovan and Rinkeby.
This a simple smart contract.
You will use ether to buy Singapore property with MetaMask.
You will see a dapp which associates an Ethereum address with property.
How to buy and sell with MetaMask.
voting using Ethere
payments using Ether, the currency of the Ethereum blockchain platform.
Concept of tokens and its usage.