General Remarks:
a)  In Latin the perfect tense is the “narrative tense”;  that is, it appears mostly in texts which describe past events and, in general, does so more frequently than the imperfect.  The perfect expresses punctual (completed) actions, whereas the imperfect describes states of long duration, repeated or attempted actions.
b)  When translating into English, there is often no clear distinction between the perfect and imperfect — laudavi can often be translated either with “I praised” or “I was praising.”  Since in English the preterite (simple past or perfect) is the “narrative tense,” the usual translation is “I praised” rather than “I was praising.”

There are differing paradigms of the perfect stem.  Hence it is impossible to predict which verbs follow which model.  As a result, for those that do not follow the “regular” so-called “v-perfect,” the first person singular must be learnt as part of the basic verb itself.

1)  The “regular” v-perfect applies primarily to verbs of the ā- and ī-conjugations, but also to some of the other conjugations:

The Perfect PASSIVE

In Latin, the passive is constructed out of two components:  out of the so-called perfect passive participle (PPP) and a present-tense form of the helping verb esse.  The formation has some similarity to the English:

Although in Latin the participle usually comes first:  laudātus sum.

For the passive, the active forms of the perfect are mostly irrelevant;  instead, when learning the “irregular” verbs, the PPP has to be memorized in addition to the present and perfect active.  Thus the so-called “four principle parts” have to be committed to memory as, for example, habeō - habēre – habuī – habitum - “to have.”  The PPP is given in the neuter singular nominative.

• it corresponds to English forms such as “(having been) praised,” “(having been) held.” “(having been) meant,” “(having been) sought,” “(having been) paid”
• it is declined as a regular “2-1-2” adjective of the a-/o-declension (like magnus, -a, -um).  Hence it has singular and plural forms as well as forms for masculine, feminine and neuter gender along with nominative, genitive, dative cases, and so forth.
• Most Latin PPPs end in –tus, –ta, –tum, a few in –sus, –sa, –sum.

Examples:  laudātus (“praised,” from laudāre), habitus (“had/held,” from habēre), monitus (“warned” from monēre), vīsus (“seen,” from vidēre),  jussus (“commanded,” from jubēre).

esse has no perfect passive participle;  The PPP of  ferre is lātus, lāta, lātum.  The principle parts to be learned, thus, are ferre – ferō – tulī – lātum - “to carry.”