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What are the difference between _from, _spender and _to address in these functions below?

function transferFrom(address _from, address _to, uint256 _value) public{/*...*/}
function approve(address _spender, uint256 _value) public{/*...*/}
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These are the functions used in an ERC20 token contract.

  • _from : original owner of tokens who can himself transfer some tokens or approve any third party/person to spend the token

  • _spender : Spender who can transfer tokens on the behalf of someone only if approved by token owner

  • _to : Address who will receive the tokens in any case.

You can visit it the complete contract here . Comments are quite self-explanatory.

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From the ERC20 specification:

transferFrom

Transfers _value amount of tokens from address _from to address _to, and MUST fire the Transfer event.

The transferFrom method is used for a withdraw workflow, allowing contracts to transfer tokens on your behalf. This can be used for example to allow a contract to transfer tokens on your behalf and/or to charge fees in sub-currencies. The function SHOULD throw unless the _from account has deliberately authorized the sender of the message via some mechanism.

approve

Allows _spender to withdraw from your account multiple times, up to the _value amount. If this function is called again it overwrites the current allowance with _value.

Basically, you can use approve to allow someone else to spend/withdraw tokens from your balance. The transferFrom method is the function that is called by that person to actually spend tokens from your account.

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