The perfect active indicative constitutes the fourth principal part for Greek verbs (the fifth principal part is occupied by the perfect middle/passive, which is taken up in Black, Learn, Chapter 13).

The perfect is a primary tense like the present and future active indicative, but (strangely enough) is formed with secondary suffixes.

The resultant endings for the perfect active indicative are nearly identical to those of the first aorist active indicative.

Observe that the main difference is that the perfect has the aspect morpheme ka (instead of the first aorist's sa). Also, the third plural perfect form will most often vary from that of the first aorist. Perfect verbs are also distinctive in that they will usually (but not always) will be characterized by a reduplicated syllable prefixed to the stem.

The perfect active indicative is made up of at least four morph slots: (1) the  reduplication morph (for variations of this, cf. Black, Learn, §70); (2) the lexal morph; (3) the aspect morph, which is ka for perfect verbs (except in the third person singular); and (4) the suffix, which will be one of the secondary active suffixes.

Observe the morph slots that constitute the following perfect active indicative forms of  lu,w:

Here are the perfect active indicative endings. 

The significance of the perfect tense is discussed well by Black (Learn §72); therefore, his discussion need not be repeated here. What we will do is briefly describe the basis ways perfect verbs can be translated.

The perfect tense usually characterizes an action that was completed in the past but also has continuing results in the present (or, stated differently, it characterizes a state of completion that endures presently).

The perfect tense is normally translated into English with the auxiliary verb "have" or "has" coupled with the English past participle (e.g., "found," "taught," "gone," etc.).

h` pi,stij sou se,swke,n se)
Your faith has saved you (Mark 10:52).

However, oftentimes when an existing state (resulting from a completed action in the past) is conveyed by the perfect tense, one may translate it as though it were a present tense verb in English:

pe,poiqa de. evn kuri,w|)
I am persuaded in the Lord (Phil 2:24).