canabots just beat me to it...
anyway i spent the time to wite this so here it is...
digital pins are both used for input/output (i/o). these work at the voltage level of the microcontroller so usually they can either output just 5v or just 0v. aswell they accept inputs of just 5v or just 0v (within tollerances).
analog ports are used to input a voltage that can be between 0v and 5v so a voltage of maybe 2.3v can be read with a microcontroller.
on the programming side, reading a digital port will produce eiter a 1 for 5v or 0 for 0v. reading an analogue port can produce a varying number. if the analog port is 8 bit then 0v will be read as 0 and 5v will be read as 255 any voltage level in between will produce a linear result on this scale so 2.5v would produce a reading of 127 on the programming side.
I would also like(if possible) some information on which is best used where and why?
it depends what you are using the port for. if you just want to turn a light on then use a digital port. if you want to read a sensor with a varying voltage then use an analog port. if you want to detect a push button switch then use a digital port.
But what should be plugged in the 5V power pins
5v power should come from a voltage regulator. first plug your batteries into the voltage regulator and then from the output of the regulator you get an even 5v (even if the battery is at 9v). this makes a stable power signal and stops 5v components from burning out. Also only plug the servos straight into atteries if you know that the batteries are 7.2v or below