man find is pretty clear about it:

   -perm mode



       File's permission bits are exactly  mode  (octal  or  symbolic).

          Since  an  exact match is required, if you want to use this form

          for symbolic modes, you may have to  specify  a  rather  complex

          mode  string.  For example -perm g=w will only match files which

          have mode 0020 (that is, ones for which group  write  permission

          is  the  only  permission set).  It is more likely that you will

          want to use the `/' or `-' forms, for example -perm -g=w,  which

          matches  any file with group write permission.  See the EXAMPLES

          section for some illustrative examples.



   -perm -mode



          All of the permission bits mode are set for the file.   Symbolic

          modes  are accepted in this form, and this is usually the way in

          which would want to use them.  You must specify `u', `g' or  `o'

          if  you use a symbolic mode.   See the EXAMPLES section for some

          illustrative examples.



   -perm /mode



          Any of the permission bits mode are set for the file.   Symbolic

          modes  are  accepted in this form.  You must specify `u', `g' or

          `o' if you use a symbolic mode.  See the  EXAMPLES  section  for

          some  illustrative  examples.  If no permission bits in mode are

          set, this test matches any file (the idea here is to be  consis‐

          tent with the behaviour of -perm -000).



   -perm +mode



          Deprecated,  old way of searching for files with any of the per‐

          mission bits in mode set.  You should use -perm  /mode  instead.

          Trying to use the `+' syntax with symbolic modes will yield sur‐

          prising results.  For example, `+u+x' is a valid  symbolic  mode

          (equivalent to +u,+x, i.e. 0111) and will therefore not be eval‐

          uated as -perm +mode but instead as  the  exact  mode  specifier

          -perm  mode  and so it matches files with exact permissions 0111

          instead of files with any execute bit set.  If  you  found  this

          paragraph  confusing,  you're  not alone - just use -perm /mode.

          This form of the -perm test  is  deprecated  because  the  POSIX

          specification  requires  the  interpretation of a leading `+' as

          being part of a symbolic mode, and so we switched to  using  `/'

          instead.