Jerusalem now which country?

Hi,
becouse not clean for me and not found correct answer so ask maybe somebody know in here.
Last year i visit Jerusalem and some people say this part of Palestine other say is Israel.
Which one real?
East Jerusalem is Palestine? Where start the Palestine area?
How check this?
If Palestine for me +1 country to the list, if no need go again.

I hope I didn't offend anyone with this question.