How to simplify or expand factors?

I'm self learning matlab and I wanted to plot a graph. I think I have missed an important fact regarding multiplication in matlab. How can I multiply something like the following?

>> x=0:0.01:11;

>> y=(x-1)*(x-2);

Error using *

Inner matrix dimensions must agree.

Answer 1

[Azzi Abdelmalek]

Use the product .*

x=0:0.01:11;
y=(x-1).*(x-2)

[Sachi]

So what's the difference? How do I know when to use ".*" and when to use "*"?