Confusion regarding indice vector?

I want to write a MATLAB function to systematically develop the sequence y[?] generated by the convolution of the

two-finite length sequence x[?] and ?[?]. Program should be able to handle causal and non- casual sequences.

Program should call for the input sequences and their indices vector?

Below is my code:

function [ny,y  ] = convolution(nx,x,nh,h )
%UNTITLED7 Summary of this function goes here
%   Detailed explanation goes here
a=nx(1)+nh(1)  %nx is time span of x and nh is time span of h
b=nx(length(x))+nh(length(h))
ny=[a:b]% ny is length of y
y=conv(x,h)
end

What is meant by indices vector in bold? Is it referring to what i have used and wrote nx and nh?