The importance to the Israeli's on passover is that the Jews came out of Egypt from slavery.
The passover was initiated on the Old Testament when the Angel of Death passed over the Israelites during the plagues on the Egyptians before the Exodus. This is found in Exodus 12. The passover feast was meant to remind the Israelites about how they were delivered from enslavement in Egypt.
Passover is not something that is sung. It is a holiday celebrated to commemorate the exodus of the ancient Israelites from Egypt.
Passover
If your question is referring to the first Passover, the Israelites were redeemed from Egyptian slavery by God, and gained their freedom. See also:More about Passover
the Israelites did not leave during passover. When they did leave it was Moses who lead them.
passover
because the pharoh's son was killed at passover.
salt water symbolises the tears of the israelites.
Pesah or passover.
In the days of the Great Temple, Jews would traditionally perform sacrifices and/or bathe in ritual waters in order to achieve a state of "tahorah" or ritual purity. While some still do bathe in ritual waters, the offering of sacrifices has not existed since the Destruction of the Second Temple in 70 C.E.
It is called a Seder, or "order" in English
The importance of Passover is that all the Israelites had been slaves in Egypt for 400 years. In the story of Passover God sends 10 plagues down on the Pharaoh and the rest of Egypt, and after the last one, the death of the first born, the Israelites were finally set free.