Matlab problem conv function

n3=0:110
u=1.*(n3>=0);
y=conv(u, h2);
subplot(212);
stem(0:length(y)-1, y);
xlabel('n');
ylabel('Convolutia liniara ya(n)=xa(n)\otimes h(n)');

Can someone explain why is conv used if i want a response at unit step of function h2?

[Jan]

What is h2 ?