I hav started a youtube channel to teach ethereum and solidity: https://m.youtube.com/channel/UCZM8XQjNOyG2ElPpEUtNasA https://m.youtube.com/channel/UCZM8XQjNOy

I hav started a youtube channel to teach ethereum and solidity: https://m.youtube.com/channel/UCZM8XQjNOyG2ElPpEUtNasA https://m.youtube.com/channel/UCZM8XQjNOyG2ElPpEUtNasA Contract call can be broken down into 2 categories: state changing vs read-only. If its a state changing contract call, it will be executed by every node on the network. In this case its considered a transaction. This transaction has to be mined in a block and cost ether. The new state will be stored on the blockchain only after the transaction has been succesfully mined. The other kind of method call is read-only. Its free, ,is executed only by a single node, and does not alter the blockchain state.