Coinbase debit
As you can see, this function is used for scenarios where owners are offering tokens on a marketplace. To use it, you will need to install the MetaMask plugin on your browser and a Rinkeby Ethereum test network account with at least some Rinkeby Ether in it. Smart contracts can be much more complex depending on your business logic, your modeling of the user interaction, whether or not you allow token minting and burning, lifecycle changes you introduce into the contract, the need for admin-level capabilities which usually comes with an admin-authorized set of functions, and so on. The humble ERC20 token specification has become the de facto standard for Ethereum tokens. Here are a few examples of such fields.