Ethnically speaking, are there more Russian and Eastern-European Jews or are there more who are originally situated from the Middle Eastern region (such as Yemenite Jews etc.)?
And are there any real differences between them (I mean things such as the pronounciation of Hebrew or religious ceremonies)?
In the first place, not all Israelis are Jewish. There is a large percentage of Israeli Arabs, those who did not leave when the Arab countries first attacked Israel in 1948.
Many Jews came to Israel around 1900 from various contries. Jews have been living in Israel since biblical times, and there have been emigrations to Israel since then, with, as I said, a large percentage emigrating around 1900.