Understanding coding terminology - indexing

I am currently going through the Matlab fundamentals course and am at the part of learning to do categories. As part of the section I'm on, it asks me to "Try indexing into y with iC and iNB" at the end of the section. It is not necessary for me to complete it to progress, however, I think it is better for me to at least understand it. As I have never formally been taught coding, I was wondering if someone could explain what the phrasing is actually telling me to do or let me know where I could find a clear text that explains it (and other coding terminology if possible!).

I tried to google but didn't find any clarity elsewhere.

Thanks in advance

[Jan]

The fragment "Try indexing into y with iC and iNB" is not enough to undestand, what you should do.

Answer 1

[Jan]

"Indexing" means to address an element of an array by using an index. Example:

x = [3,1,4]
index = 2
x(index)   % reply: 1

This replies the 2nd element of x.

Answer 2

[锐]

It should be y(iC) and y(iNB)...