In the Command Window, we see: >>: This notation >> is called the prompt.
In the Command Window, MATLAB can be used interactively. It means that MATLAB command or expression can be entered, and MATLAB immediately responds with the result.
For example, this is the way it would appear in the Command Window:

>> mynum = 10
mynum =

MATLAB uses a default variable named, if an expression is typed at the prompt and it is not assigned to a variable. For example, the result of the expression 9 + 3 is stored in the variable ans.
>> 9+3
ans =