Question

what is a controlled experiment? All the explainations online are confusing

Answer 1

Do you know about "variables"?

Like the Independent Variable,
and the Dependent Variable?

In any experiment,
we are supposed to change the variables, to see how it affects the whole experiment. To see what kind of difference it makes.

In a "controlled experiment,"
we only change ONE variable at a time.

We change ONE variable.
We look at how it affects the experiment.
And then, we put the variable BACK THE WAY IT WAS,
and we change a different variable.

That's a "controlled experiment."
We change only ONE variable at a time.