An andiron is an L-shaped iron bar used in the fireplace to hold wood. They come in pairs and logs are laid across the horizontal portion, in order to build up a fire. Getting the wood up off the ground allows more air to pass under the logs, reducing the amount of smoke. The vertical portion is there to catch the logs in case they settle and decide to roll.
These are usually made of cast or wrought iron (though the ones below are mostly brass). They’re footed, and some of the better (and older ones) have legs that are actually in the shape of legs! They may have clawed feet on the end, too. Some of these can be extremely ornate.
P.S. Happy Halloween to everyone out there planning some spooky or silly fun tonight! Eat lots of candy!!