Array vs buffer


hi everyone 

i hope someone could help me with this problem.

I am doing a project using XCODE where i have to split a audio signal into two and add them back together afterwards. 

One will be the original audio and the other will be a processed audio(filtered)

Do i have to use arrays to do this process or can i use buffers since i have already used them in my project.

or are they the same thing? im so confused with all the terms. :(