could you possibly enlighten me about any differences between 2 sentences below:
(a) I went to Warsaw this year.
(b) I have been to Warsaw this year.
Thank you very much in advance!
If it is nearing the end of the year, then it is permissible to say:
(a) I went to Warsaw this year.
In this case you conceptualize the year as being over or past in terms of the possibility of going to Warsaw again. So the past tense is fine. This is similar to you saying to your wife when you arrive home after work:
I saw John today.
Although today is not finished, you are not expecting to leave the house again, so you conceptualize the chance of seeing John again as over or past.
Sentence b:
I have been to Warsaw this year
could be said at any time during the year, and is stated as one of the things you have done, with no implication as to whether or not you think a further visit is possible.
Sentence (a) is in the simple past tense. "I went to Warsaw," "I threw the ball," "I blew my nose," "I saved some money," "I kicked the dog"--all these sentences have verbs in the simple past tense.
On the other hand, your second example, (b), has a verb in the "present perfect" tense. "I have been to Warsaw," "I have thrown the ball," "I have blown my nose," "I have saved some money," "I have kicked the dog"--all these sentences have verbs in the present perfect tense.
They say from the perspective of the present what you have done in the past. You imply that of the many things you have done in the past, you have done this particular thing--went to Warsaw, blew your nose, saved your money, or kicked the dog. You can check these things off the list of things you have done.
See http://www.youtube.com/watch?v=_8ObuO5neR0 for a lesson on the differences between the present perfect tense and the past perfect tense.
The simple past tense is just that: simple. You did this, you did that, you did the other thing. Period. Was it Julius Caesar who said,
"I came. I saw. I conquered"?
In the present perfect, the quotation would be
"I have come. I have seen. I have conquered."
Both of my examples have a certain "ring" to them, but the first example is much more succinct--and shorter by about 13 letters!