What is the difference between parameters and variables?

Parameters are the named inputs that a function or method declares in its signature. They are placeholders that receive values when the function is called. Variables, on the other hand, are storage locations that can hold data at any point in a program. While every parameter is a variable, not every variable is a parameter. Parameters have a limited scope (only inside the function) and are typically immutable unless explicitly modified. Variables can be defined anywhere in the code, have broader lifetimes, and can be reassigned freely. For example, in JavaScript: function add(a, b) { let sum = a + b; return sum; } Here, a and b are parameters; sum is a local variable.