So it's an alternative to toilet paper?

For women peeing, yes. When shitting it's mainly for completion.

What?

That's not the english word for it? You simply wipe first and then use the bidet to make it even cleaner, surely you got that?

I think you were just a little too vague due to a dangling modifier (pun only slightly intended).

Essentially, "what was being completed using the bidet?"

But what does the bidet do, how do people use it!? They shove it in their buns?

Well, if that question came up then we may have a slightly different meaning for the word over here.

Still, the obvious answer is that the wiping/cleaning was completed.

Edit: @Blkfish  It sprays water up your crotch.

It's not exactly a question that came up. Your use of the word in that sentence carried an unintentional interpretation that was the dominant one for anyone who has never used a bidet (myself included) - once I stopped to think about it, I realised what you actually meant... but the way it's worded, it sounds like you start off "shitting" in the toilet, and then complete the process of "shitting" in the bidet. Hence the "What?"

Now, obviously it's actually an absurd idea, finishing off that particular process in a different bowl... but that's how it reads.

I was answering the question "So it's an alternative to toilet paper?" though, which made me think that the message was clear.

That's some funny shit nonetheless xD

Where we use it, we use paper first, to remove easily the most without touching it, then we wash with the bidet to clean ourselves better.
Obviously it's possible to wash your ass and dick/pussy in other ways (and to wash just the dick nothing can beat the washbasin for ease), but bidet makes it easier and more comfortable when you are dressed. A toilet bowl with built-in bidet can be as easy and comfortable, but a separated bidet make it more difficult that the tap or nozzle become accidentally dirty.
Even more comfortable and easier can be having a shower or bath tub with flexible shower head near enough to the toilet bowl, but it isn't always possible.