Please define "present perfect tense" with few examples.

The Present Perfect Tense connects the present to the past. It describes an action that happened in the past and goes right to the present moment. The time of occurrence of the action is not mentioned. Usually, the time is not important or is not necessary to know. It is the result of the action that matters. It tells us the outcome to date of the action. E.g., "Frank has gone" tell us that Frank is no longer with us.

To express something in the present perfect tense, join the present simple tense of have/has with the past participle of the main verb (which can be a regular verb or irregular verb).
have/has + past participle

The Present Perfect tense is used:

• for an action that happened in the past and the time of occurrence is not stated or implied.

Example: I have written a book about spider webs.

• for an action or situation that began in the past and continues to the present.

Example: He has been in prison since 2000.

• to express repetition of an action at unspecified time in the past.

Example: She has already had a few quarrels with her neighbour.
Example: I have been to the circus a few times.

• for an action occurring within a specific time period that is not over

Example: I have had three cups of tea this morning. (It is still morning and I may have another one
or more cups of tea before the morning is over.)

• in news reports

Example: Negotiations with the insurgent forces have broken down.

• with phrases beginning with "This is the first/second/third ....time"

Example: This is the first time I have won the jackpot.
Example: This is the fifth time I have lost my job.

• to answer questions that are asked in the present perfect tense.

Example: "Where have you been?" "I have been to London to see the Queen."
Example: "What have they bought?" "They have bought a couple of rifles."

• with ever and never. Ever is used to ask if any things have or have not happened at any time up to now. It is also used in negative statements and together with the phrase "The first time ..." Never is used mainly in negative statements. Their position is just before the past participle verb.

Example: Have you ever lost your temper in a public place?
Example: That's the biggest lie I have ever heard in my whole life.
Example: This is the first time we have ever listened to such a dirty joke.
Example: We have never been to a circus.

• with other time expressions such as:

always: He has always believed everything he reads.
how long: How long have you waited for the bus?
recently: I have only recently started learning English.
lately: I have met her a lot lately.
so far: We haven't had any trouble with the new tenant so far.
Up to now: Up to now we have not come up with a solution to the problem.

'For' and 'since'
When an activity began in the past and is still going on, we use the present perfect tense + for/since.
We often use for and since with the present perfect tense. Since can only be used with perfect tenses (present perfect and past perfect tenses); for can also be used with the past simple tense.

• We use for + a period of time as an indication of how long an activity has lasted up to the present moment.

Example: We have been tennis partners for three years. (NOT: We are tennis partners for three years.)

• We use since + a point in time in the past to show when in the past the activity began.

Example: I have become her tennis partner since early May this year. (NOT: I am her tennis partner since early May this year.)
Examples:
He has lived here for five years. (he is still living here)
He has lived here since 2000. (he is still living here)
INCORRECT: He lived here since 2000./He lives here since 2000./He is living here since 2000.

Just, already and yet
We often use some words with the present perfect tense. These words include:

• Just: if something has just happened, it happened only a short time ago. Just is usually placed after have/has and before the main verb in a sentence.

Example: Sister Jane has just been out shopping.
Example: I have just finished painting the ceiling.
Example: He has just drawn a picture of an owl's eye.

• Already: if something has already been done, it's done by or before now or a particular time. It is usually positioned in the middle (after have/has and before the main verb) or at the end of a sentence. It can also appear in questions.

Example: They have already built the tallest sandcastle on the beach.
Example: What did he say? I've forgotten already.
Example: Have you already made a police report of the accident?
Notice no mention of when an action took place.

• Yet: if something is not done yet, it is not done until now or until a particular time. We usually use yet at the end of a negative sentence or a question.

Example: They have not yet come.
Example: Has the train arrived yet?
It is possible for yet to appear in the middle of a sentence.
Example: As yet, we've had no word from them. (OR: We've had no word from them as yet.)

have/has gone ; have/has been
See the difference of meaning:
They have gone to Timbuktu. (They are still there or on the way there.)
They have been to Timbuktu. (They are not there now. They have come back or are somewhere else.)

HOPE YOU UNDERSTAND!!