Question: Does encodeABI() just do a decimal to hex encoding or is something more going on under the hood?

<http://web3js.readthedocs.io/en/1.0/web3-eth-contract.html#methods-mymethod-encodeabi>

Answer: 
this function gives you the encoded ABI form of a function and its parameters, it will be helpful if you are constructing a raw transaction or to send this form in a sendtransaction or call exp :

```
eth.sendTansaction({from:primary, data: your_function.encodeABI()})

```
There is more to the encoding tan just hexing.  

The details of what is going on under the hood are explained here:
<https://solidity.readthedocs.io/en/develop/abi-spec.html#>  

<https://github.com/ethereum/wiki/wiki/Ethereum-Contract-ABI>