man find é bem claro:
-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.