The Present Perfect

The Present Perfect Simple

When we use the Present Perfect simple in a sentence we focus on the completion of an action, which gives information about the present state of things. The moment in which the action is performed is not important, so it is not mentioned:

I have painted the room green

=

now the room is a different color

She has made the cake  

=

now there is a cake

Have I met you before?  

=

do I know you?

Have you eaten anything?

=

are you hungry?

I’ve broken my leg   

=

my leg is broken

Therefore it is often used to:

Break hot news, regarding an event that is fresh and has not become normal yet, when we think that the completion of the fact changing a present state of things is important for the listener and they don’t know or we think they don’t know it yet:

Jenny has passed her exam
Bob has been promoted

If it has happend more than once then we may or may not specify the period. The word PERFECT in grammar means "past", and the word PRESENT means... "present", so we also use that "informative" function of the present perfect to talk about an action that has been completed one or more times in an unfinished period that straddles the past and the present which could be our entire life, a year, a week, ecc., and that leaves open the possibility that it may be performed again in future. When it's used it's similar to saying "up to now" or "so far":
I have been to the gym 3 times this week (Today is Wednesday, period = from Monday to now, includes past and present. This week has not finished so I may go there again)
He’s written 16 books. (period=his life, he started writing books at some time in the past. So far, he has written 16 books. (he has not stopped writing and there's no reason why he should stop, so he may write more books).

The Present Perfect Continuous

Focuses on the continuity of an action completed repeatedly or performed uninterruptedly up to the moment of speaking and whose performance is considered unfinished, unless it is ended as a result of a contingent action, so it is used to ask or say how long:

I’ve been decorating the house this summer. The focus is on the action (decorating) which is unfinished.

I’ve been reading that book you lent me. I’ve got another 50 pages to read.

I’ve been calling Linda all day but she isn’t answering the phone

Here you are! I’ve been looking for you all day (the action stops because I’ve found him)

It's also used to speak about actions we see as temporary:

I usually work in London but I’ve been working in Birmingham for the last 3 weeks.

With static verbs it is necessary to use the simple form.

Thanks, I’ve been lost all this time (but now I’ve found you, so the action has stopped)

This is also true with the negative form

I have not heard from Liza all this week

Unless we need to contradict an assumption or express the opposite of a normal situation

I haven’t been studying science, but maths

I haven’t been feeling too well today

It may also be used with verbs which are treated as such, like work, smoke, collect and play, (to avoid being wrong better use them always in the continuous form)

I have lived in Milan since 1996 (uninterrupted action that may stop now or go on into the future. Period = 1996 – now, includes past and present)

If you use “since” and “for” the present perfect simple is the same as present perfect continuous.

The presenter has been speaking for 45 min.

The presenter has spoken for 45 min.

If I say

The presenter has spoken (without “for”),

the action’s finished (the action is important, the time is indefinite, it’s not important)

It’s better to use the present perfect continuous when we want to focus on how long