What part is this? (axle)?
that is not your axle. Your axle is above where you circled that tubular bar commming out of the black rubber boot is the axle. What it looks to be is the connection of the sway bar. Its hard to tell without seeing what that piece connects to. If it is the tie rod do not drive on it. But it looks connected to the lower control arm so im guessing sway bar link which you should get fixed soon
You have a loose worn sway bar end link. Easy and cheaper to replace than a half-shaft. It's not part of the steering mechanism as the steering arm that connects to the spindle and tie-rod end is located behind this picture.
Is the other end connected to a pivot on the frame? It looks like a torsion bar. (often called a sway bar) It should have a bushing that it pivots on at each end. (often with rubber grommets to stop squeaks) If the bushing is gone/bad, the bolt will bounce around in the bracket and eventually break. If it breaks, the entire wheel assembly will break away pulling the axle shaft (front half drive shaft from the looks of it) with it. This will allow the wheel to pivot on the ball joint (the lower connection in the picture) and basically crash the truck! I wouldn't recommend doing anything until that is fixed. If the hole for the bushing and bolt are not torn up, you can buy a new bushing for a few $ and do the repair yourself. If the remaining parts are damaged, it might require some machining or new parts besides the new bushing. It would have helped a bit knowing what vehicle it was on. It is rather hard to tell if it is a front wheel drive car, the front axle on a 4 x 4, or the rear axle on an independent suspension vehicle. (My guess is the 4x4 due to the height, but) For the person who says the axle is coming out of the rubber boot: That is a half shaft, that comes out of a transaxle or front differential. The big square steel piece at the bottom that the circle is above is the axle.
