Mahmoud Ahmadinejad is a man from a country called Iran. He used to be the leader of Iran, kind of like the president. Iran is a country that is not friends with Israel, which is another country in the same region.
Ahmadinejad has said things that people think are not nice about Israel. He thinks that Israel should not exist as a country because he believes that it is a bad idea for Muslims and Jews to live together.
Because of these things that he said, many people in Israel and other countries feel angry or scared of him. Some people think that he wants to hurt Israel, but others think that he just doesn't agree with how Israel is being run.
Overall, there are a lot of complex issues between Mahmoud Ahmadinejad and Israel that are not easy for even grown-ups to completely understand.