To explain this, we'll go back to the Holocaust, when Hitler called for millions of Jewish people living in Europe to be killed.
Many Jews fled Europe, and were given a large part of Palestine, which became known as Israel.
Those Jewish people who moved to the new country became known as Israelis.
The Arab people - or Palestinians - who already lived there didn't accept the new country, and both sides went to war.
In 1967, the Israelis took control of an area in Palestine called Gaza - or The Gaza Strip - which it wanted to hold on to until both groups of people agreed to live in peace.
Israel agreed to let go of control of Gaza in 2005, but in 2006 Hamas, a group which many people view as a terrorist organisation, came into power.
Hamas refuses to recognise Israel as a country and wants the Palestinian people to be able to return to their old home - it's admitted using violence to get what it wants.
Over the years, there have been waves of violence.
This latest conflict began when three Israeli teenagers, hitchhiking home from a Palestinian area, were kidnapped and murdered.
Here in Ireland, a trade union representing retail workers has asked supermarkets to stop stocking Israeli produce.
Mandate says it has contacted chains like Supervalu, Tesco, Lidl and Aldi.
Pro-Palestine groups are calling on people to take part in a non-violent international pressure on Israel to try and bring about peace.
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