问一个非常弱智的问题,大家不要嘲笑我

I guess you mean why I said "Extracted" is a past participle? Hope the following  information will be helpful to you:

the past participle is usually a passive participle (but sometimes not: in particular, the past participles of intransitive verbs are never passive, and are therefore sometimes used with active senses, such as in the expression fallen comrades).

in some sense, the past participle functions as the adjective. as to the the past form, it is usually used to mean that the action happened in the past.