What does 'safely' mean in man mktemp?

[Peng Yu]

Hi,

man mktemp says "Create a temporary file or directory, safely, and
print its name."

I'm wondering what it means by "safely".

Does mktemp test if there is already a tempfile with the given name?
If there is indeed with the same file name, will mktemp use a
different name rather than overwrite the one with the original name?

-- 
Regards,
Peng