What do philosophers mean by the term 'mental content'? My initial reaction to the phrase was to take it to mean something like 'the meaning of a thought, belief, etc.' But this interpretation seems...unexplanatory. It seems to me that things don't just MEAN; rather they mean TO some individual/group. (X doesn't just mean Y; X means Y to Z.) For any given thought/belief/whatever (X), we could imagine infinite different Zs, and through these Zs, infinite different Ys. Which Zs are the relevant ones? Why is whatever distinction is drawn between relevant and irrelevant Zs drawn as it is?
Or is my vague conception of mental content as the meaning of a thought, belief, etc. not in line with how philosophers use the term? If so...what do they mean by it?