why variable substitution is so different?

there are two files in current dir

[root@workspace tmp]# lltotal 8-rw-------. 1 root root 6 Mar 31 13:18 *-rw-------. 1 root root 6 Mar 31 13:18 ?[root@workspace tmp]# for f in "`find . -type f`";do echo "$f";done./*./?[root@workspace tmp]# for f in "`find . -type f`";do echo $f;done./* ./? ./* ./?

I am confused about the output of the two echo ...

the differenct is: the double quote around the $f

why the outputs are so, anyone can explain this?

thanx any help in advance.