The Past Participle has no particular meaning of its own. It is used in several different constructions which have different meanings.
- It is used after have (has, had, haven't, hasn't, hadn't) to form perfect constructions, which refer to past actions with present relevance. The exact meaning of this "present relevance" can vary - it might mean that the action is continuing to the present; or that it has finished very recently; or that its effects or results are still salient. Examples:
I have seen her.
We hadn't left yet (when something happened)
- a) It is used after to have to form a past infinitive. (I list this separately from 1 because this use does not necessarily have a specifically "perfect" meaning):
We hope to have finished by 10.
- For transitive verbs, it is used with be (am, are, is, were, was, being, been) to form passive constructions. These can be in any tense, depending on the part of be used:
Cars are built in that factory.
With that microphone, you will be heard.
The game was stopped when a cow ran onto the pitch.
The cakes had all been eaten.
The boxes are being packed right now.
- a) Colloquially, we sometimes use part of get instead of part of be for the passive:
The cakes got eaten.
- For many verbs, it can be used as an adjective. The precise meaning varies, but is usually about the result of the corresponding verb. It can be used predicatively:
The meat is cooked.
They brought out the cooked meat.
Sometimes it is difficult to determine whether a past participle is being used as a passive or adjectivally. It is usually the tense that tells us. In the example above,
The meat is cooked.
could be passive, but if it is, it is a simple present, which generally refers to a timeless or habitual condition. So if we were talking about a factory making pies, for example, where they cook meat every day, we might say the meat is cooked in these ovens, and then transferred here to be placed in the pies.
But if we were talking about a particular piece of meat, that would be odd in that meaning, because we usually express activities happening at this moment by a continuous construction, so we would say The meat is being cooked.
So in this context, The meat is cooked is much more likely to be interpreted as an adjective: The condition of this piece of meat is that it is cooked, rather than raw, or frozen, or half-cooked.