Yes, Servos are interesting because you have to keep telling a servo over and over what its position should be. That is how it knows to keep moving until it reaches its desired destination.... its also why it fights for position when it is "still"... if you take your finger and try to move the servo horn it will fight against you and move back... that is because the circuit is constantly telling the servo where it needs to be.... at least this is how I understand it to work. Google is probably your best bet.