Where and what is the name of log files of bitcoind?
If I make a command like "sendtoaddress", will the command and the arguments (like the amount of bitcoin I sent and which address I sent) all be logged?
The default data location of bitcoind is ~/.Bitcoin on unix and %APPDATA%\Bitcoin on windows. In it, bitcoind will write a debug.log file which is automatically trimmed every once in a while. I'm not sure what is in it, but it should be easy to check. You can also start bitcoind with a commandline parameter to send its debug info to stdout, if you wish.