This is a great question. A little background information might be helpful here. The Israelites are in slavery in Egypt, because Pharaoh was afraid of their numbers. When the Israelites cried out to God, he heard their voices and raised up Moses and Aaron to go and deliver his people.
He accomplished this deliverance through ten plagues. Each plague was passed, because of the hardness of Pharaoh's heart. The ten plagues are as follows:
(1) The rivers and other water sources turned to blood killing all fish and other water life.
(2) There is proliferation of frogs over the land.
(3) There is a proliferation of lice or gnats on the land.
(4) The land is filled with flies.
(5) There is disease on livestock.
(6) Boils appear on livestock and people.
(7) There is a huge hail storm that destroys the land and livestock.
(8) There is a plague of locusts.
(9) There is darkness over the land
(10) God brings death of the first-born over Egypt.
Finally, it should be stated that the land of Goshen, where the Israelites live is left intact.