Programming bluetooth android to arduino- What should I learn?

Im trying to control multiple servo's and/or multiple leds with an app made in app inventor. Where Im stuck is how to communicate between the two. How would I program the arduino to control servo #2 instead of servo #1 or led #2 instead of led#1 when a button is pressed on the android app? Do I use char, for loop, strings, bytes, events? Im lost. Can someone point me in the right direction?

Can someone point me in the right direction?

That way! No, no, the other way.

Some context about your application(s) would be useful.

How would I program the arduino to control servo #2 instead of servo #1 or led #2 instead of led#1 when a button is pressed on the android app?

When a button is pressed in the Android application, what are you sending to the Arduino? How is the Android application supposed to know whether the data is for servo/led/whatnot one vs. servo/led/whatnot two?

If there are two buttons/sliders/input fields/whatnots on the Android application, one for each servo/led/whatnot, then the data sent to the Arduino should reflect which button/slider/input field/whatnot the data came from, and the Arduino should use that to determine what servo/LED/whatnot to apply the data to.

It ain't rocket surgery.

Do I use char, for loop, strings, bytes, events?

Yes. Wait, no.

Im lost.

I've got a map here. I'm willing to tell you where to go.

AllenI:
How would I program the arduino to control servo #2 instead of servo #1

Send the Arduino a '1' or a '2' whenever you send a servo position.