It doesn't exactly clone the argument. It does, however, only use it for &self methods
#ownership question
covert mural
(namely, the fmt method of the appropriate formatting trait)
No.
The functionality of the fmt methods, in general, is to write the given value to a given buffer. format! creates a string to act as a buffer and then returns it after the write.
If you write a string to a string, the effect is equivalent to what clone would have done
But no clone was actually ever called, technically.
It's... Slightly more involved, but the basic idea is there.
It derefs the string to a &str, then it copies all of its bytes into the new buffer, then it returns the buffer
This is also what clone would do, so they end up doing the same thing
A "buffer" is generally a term for "temporary storage" or for "a block of memory". In case of IO, it's usually a block of memory, generally represented as one of Vec<u8> or &[u8] or &mut [u8] depending on what you're doing with it.
For format specifically, it's a String, because it knows you're writing through the std::fmt APIs instead of the std::io ones, and those are string-based.