The passive participle (or perfekt particip) is normally used to say that something has happened to an object, and that the action is finished. So it has both a passive meaning and a past tense meaning.
There are a few patterns for how they are created, e.g.:
Verbs ending in -ar get the participle ending in -ad. E.g. irriterar -> irriterad ('irritate', 'irritated')
Verbs ending in -er get the ending -d E.g. stänger -> stängd ('close', 'closed'). If the root ends in a voiceless consonant (s, f, k, p, t), the -d is changed to -t instead.
Strong verbs get the ending -en E.g. stjäl -> stulen ('steal', 'stolen')
The passive participle behaves like an adjective: it changes for number and gender.
If the common gender form ends in -ad, the neuter form will be -at and the plural -ade. E.g. överraskad, överraskat, överraskade.
If it ends in -d, the neuter will end in -t and the plural in -da: stängd, stängt, stängda
If the common gender form ends in -en, the neuter form will be -et, and the plural -na. E.g. uppäten, uppätet, uppätna
/ fluent 
/ learning 
/ fan of 
(bs/bl)