The closest thing I can think of in English would be: "it has been done" / "this has been done already" - where you are focusing on the fact that the action is complete rather that on who has performed it. There is, however, a verb in this type of sentence (pojechano <- pojechać, zrobiono <- zrobić, namalowano <- namalować), what is missing is the subject, so in essence you do not express WHO has gone / made / painted.

These words mean that someone or something (we don't know the subject in a sentence) has done something. for example: Namalowano obraz. - The picture was painted (something like that - the more exact translation is: Obraz został namalowany) The action is finished but we don't know who did it.