Helvetica already made a great explanation but here is my take on it as well..
When this card pops up as feelings in relationship spreads..for me- it means wild fantasies which usually contradict the civilized "thoughts" making the *subject person* go a bit lunatic in their hearts/minds/souls-it's like when women have their pms-they go a bit off and overboard in feelings and actions with all those hormones rising up-we get uncontrollable and unbearable lol (i do lol)
*Hysteria* is the word i kinda relate with this card..
Btw when i say wild fantasies-those might not be necessarily only sexual-can be countless things as Moon is mysterious and represents everything hidden-making this card unique for each person..
There are sure many things under surface which you are not aware of as feelings...And when i see this card in such positions i would probably say that the person-as Helvetica says- feels one thing one day and another thing another day-and he has no control over whatever he's feeling...
I've also seen this card as: "I just don't know what i am feeling about this person" meaning -losing track with reality-not having clear thoughts and a path..
But my personal interpretation is-this person does indeed have feelings for you both sexual and probably a bit romantic as moon is sooo romantic
-but as the moon changes phases his feelings might as well change phases-during day and night?One day he might think he is in love the other day he might think it was nonsense..he is probably strangled by all those feelings as well
So just be careful ok?? I wouldn't take this card as a reliable stable situation
But
Those are
Just some thoughts..