As a follow up to my DIY Arduino Oscilloscope video or as a stand alone tutorial, this video should help you understand arrays and recursion in Arduino. You can find the original post here: DIY Arduino Oscilloscope with the Nokia 3310 GLCD screen
An array is like a variable in that it stores data but it can hold a lot of different pieces of data, not just a single value like a variable.
Recursion is a method of repeating some lines of reusable code to accomplish a repetitive task with as few lines of code as possible.
Here is the sketches and library used in the video: ArduinoOscilloscopeRecursion