Only Skull and Cross have 100% correct meaning - others may differs from group compilation and Your choice.
Most popular (of what I have seen / used without misunderstanding) :
Moon - Mage poly
Square - Hunter trap
Star - Rogue sap
Orange nipple - Druid hibernate
Purple - Warlock fear
But if You will mark Star and tell mage to poly that he will probably do it, so there is no 100% defined. Usually square and moon are cc'ed as soon as You mark them and 99% works without problems.