Have a look at this situation.
Tom is looking for his key.
He can’t find it.
He has lost his key.
What this situation shows is that Tom recently lost his key and he still does not have it.
have / has lost is the present perfect.
The present perfect is have/has + the past participle (third form). With regular verbs, it ends with -ed. With irregular verbs – well you just have to remember them.
The present perfect is used when there is a connection with now! (present = now). The action in the past has a result, consequence now.
You can also use the present perfect together with the words just, already and yet.
Just = a short time ago.
already = something happened sooner than expected.
Yet = you are expecting something to happen (questions and negative sentences only).
Are you hungry? No, I have just had lunch.
Hello, have you just arrived?
Don’t forget to send the letter.
I have already sent it.
What time is John leaving?
He has already left.
Has it stopped raining yet?
I have written the letter, but I haven’t sent it yet.
The difference between gone (to) and been (to)
Mary is on holiday. She has gone to England. (= she is there now or is on her way there.)
Mary is back home now. She has been to England. (=she has now returned)