The full form of "I'd" is "I would", which means I want, I hope, I am willing. Similarly, "I'll" means "I will".

The specific usage of I'd, that is, I would, is followed by the original form of the verb, the original form of be, or have done. For example, I'd like to travel by train, which means I want to travel by train.

The word "would" has the same properties as can, must, will, etc., and they are all modal verbs. Modal verbs themselves cannot be used as predicates, so when such modal verbs appear in a sentence, the prototype of the verb needs to be added to form a predicate.

Examples of "I'd":

(1) I'd like to learn a new language.

Translation: I want to learn a new language New language.

(2) I'd like some milk.

Translation: I want some milk.

(3) I'd like to know the truth.

Translation: I'd like to know the truth.

（4）I'd be grateful if you could.

Translation: I would be very grateful if you could.

(5) I'd have told her the answer.

Translation: I should tell her the answer.

Reference for the above content: Baidu Encyclopedia-English abbreviations