Contraction " 'd " or not (e.g. I'd say/think)

Please tell me the difference in:

" 'd "


not " 'd "

EX: I’d say/imagine/think… vs I say/imagine/think… (Many people in this forum wrote I’d say).

I’d like/love/prefer… vs I like/love/prefer…


PS: Dear moderators, sometimes, you also write " 'd ",
I don’t know what it mean.
In the dictionary, people say ’ 'd " is used to give opinion that sb is not certain about.
Or do you imply other ideas when writing " 'd "?
Many thanks.

The contraction 'd can represent would or had.

I’d say = I would say
It’d be better = It would be better
You’d better = You had better
I’d already left = I had already left.

In I would say vs I say, the former expresses an uncertainty primarily for the sake of politeness. I would say [if you permit me]; I would say [if I were more confident of my humble facts].