what exactly are you referring to?
Generally with email clients; Inbox is the default folder for
unread emails to be downloaded into and stored, even after
they have been read.
With hotmail, spam, also known as junk, is automatically moved to the "spam" folder if someone has marked the email
messages' sender as someone who sends junk mail or
sends the same email out to several people at once who the
sender generally actually doesn't know. Usually this is some
form of advertising or money-making scheme.
But then again, you could be referring to something else.
If you are, please explain yourself further.