Other forms: stepladders
A stepladder is a folding ladder that stands on its own. Two hinged halves, and a little platform at the top.
It is what you use indoors, since a ladder needs a wall to lean on and a stepladder does not, which makes it the tool for changing a bulb or reaching a high shelf. The top step is famously not a step, and everybody stands on it anyway. The word is one word or two. British English also says steps, as in fetching the steps from the garage.
1nounstepladderA short self-supporting folding ladder.
“She fetched the stepladder to reach the top shelf.”