Ether transfer

Assuming the account you are using as sender has sufficient funds, sending ether couldn't be easier. Which is also why you should probably be careful with this! You have been warned.

eth.sendTransaction({from: '0x036a03fc47084741f83938296a1c8ef67f6e34fa', to: '0xa8ade7feab1ece71446bed25fa0cf6745c19c3d5', value: web3.toWei(1, "ether")})

Note the unit conversion in the value field. Transaction values are expressed in weis, the most granular units of value. If you want to use some other unit (like ether in the example above), use the function web3.toWei for conversion.

Also, be advised that the amount debited from the source account will be slightly larger than that credited to the target account, which is what has been specified. The difference is a small transaction fee, discussed in more detail later.

Contracts can receive transfers just like externally controlled accounts, but they can also receive more complicated transactions that actually run (parts of) their code and update their state. In order to understand those transactions, a rudimentary understanding of contracts is required.