In this dictionary, the modal verb "would" has 14 meanings.
Ok, let see this very short conversation:
A: I'm going to the cinema tonight. Do you want to come along?
B: Yes, I do.
A: That would be very interesting / That will be very interesting.
Ok, let see the sentence "That would be very interesting". According to the above dictionary, that sentence should belong to a conditional sentence type 2 "That would be very interesting if you came along". The conditional sentence type 2 expresses something that is not possible to happen at the present time or in the future.
So, if A say "That would be very interesting", it could be that he thinks that it is impossible for him to come along.
Ok, let see the sentence "That will be very interesting". According to the above dictionary, that sentence should belong to a conditional sentence type 1 "That will be very interesting if you come along". The conditional sentence type i expresses something that is possible to happen at the present time or in the future.
So, if A say "That will be very interesting", it could be that he thinks that it is possible for him to come along.
So, which one to choose "I will be very interesting" or "It would be very interesting"?
I think "It would be very interesting" is more polite, but I don't know why?.
So, conditional sentence type 2 is more polite than conditional sentence type 1?