The perfect aspect is used to talk about an action that happened before a focus time. The focus time can be past, present or future. The action is connected to the focus time. So, the perfect aspect tells us that the focus time is like this because of something that happened before.

An example

In the present perfect, we are saying that now is different because of something that happened sometime before.

I have eaten lunch.

This sentence says that I ate lunch before (eaten), but it does not say when.  It implies that now, I am not hungry: I have eaten. The present perfect is a comment on now, as a result of the past. If lunch time was long ago, I would use the simple past:

I ate lunch.

The simple past disconnects us with before. It makes the event seem like a long time ago. There is no connection to now, like there is with the present perfect.

The Three Perfect Tenses

Simple perfect tenses take the same general form using:

1. "have";
2. and the past participle (Learn more about the P.P.).

This is the general pattern:

Usually, the past participle is made with [VERB]+ed, but sometimes the past participle is irregular. You should study the irregular past participles and master them. They are some of the most common verbs in English.

Notice these points:

• Change "have" to show time: past, present or future.
• "Have" is a grammar word here; an auxiliary verb.
• The past participle of the action does not change.
• The past participle shows the action.

The Continuous Aspect and Perfect Tenses

Recall that the continuous (or progressive) aspect of a verb uses this pattern:

In the continuous versions of the perfect tenses, we mix the perfect (have) and the continuous (be [verb]+ing) together. There are three parts:

1. "have";
2. plus the P.P. of "to be";
3. and then [VERB]+ing (present participle) of the action verb.

Together these three parts have the same general pattern:

The perfect continuous aspect mixes two points: the perfect aspect and the continuous aspect. The key is to change "to be" to "been": it is how we join these two points together.

The perfect aspect and the continuous aspect mix in the middle.

Notice these points:

• Change "have" to show the tense: present; past; or future. 
• "Have" is a grammar word here: an auxiliary verb.
• "Been" is also a grammar word here: it is the P.P. of another "to be" (see auxiliary verbs).
• The present participle does not change (see present participle).
• The present participle shows the action (see present participle).

The Passive Voice and Perfect Tenses

Recall that the passive voice of a verb uses this pattern:

In the passive versions of the perfect tenses, we mix the perfect (have) and the passive (be + P.P.) together. There are three parts:

1. "have";
2. plus the P.P. of "to be";
3. and then the P.P. (past participle) of the action verb.

Together these three parts have the same general pattern:

The perfect passive voice mixes two points: the perfect aspect and the passive voice. The key is to change "to be" to "been": it is how we join these two points together.

The perfect aspect and the passive voice mix in the middle.

Notice these points:

• Change "have" to show the tense: present; past; or future.
• "Have" is a grammar word here: an auxiliary verb.
• "Been" is also a grammar word here: it is the P.P. of another "to be" (see auxiliary verbs).
• The past participle of the action verb does not change (see past participle).
• The past participle at the end shows the action (see past participle).