equality = nod to a horse = wink at a horse
inequality !=, < , > cost of a wedding > cost of a date
implication => sun is down => sun will come up
membership in (as in a set) glen beck is a member of comedians
exclusion from (as out of a set) glen beck is not a member of the thinking class
essentially, it means some comparison between quantities or entities.
but then, i'm just a software guy. let a math guy or gal get more formal with you, if they like.