What's the context in which you see that term? There are at least three different meanings for that term, though two of them are somewhat related.
- Handle as related to graphics? Start with this documentation page. Graphics handles let you manipulate graphics objects on screen; for example if I have a line's handle I can change its Color property and so change what color it is.
- Handle in terms of object-oriented programming? See here, though this is often thought of as an advanced skill for MATLAB programming. Graphics handles are handle objects, though not all handle objects are graphics objects.
- Handle as related to evaluating a function, like with an ODE solver or optimization routine? Those are function handles, which are useful in passing a "reference" to function A into function B so that function B can call function A with input arguments of its choice.
Find a zero of the function y = sin(x). Start looking at 1. fzero will call f with points of its choosing as it looks for a solution.
To check, evaluate the function handle yourself at the point fzero found.
That's pretty close to 0.