Exodus 16, Manna from Heaven – God Provides for His People, what is it.

Bread from Heaven
16And they journeyed from Elim, and all the congregation of the children of Israel came to the Wilderness of Sin, which is between Elim and Sinai, on the fifteenth day of the second month after they departed from the land of Egypt. 2Then the whole congregation of the children of Israel complained against Moses and Aaron in the wilderness. 3And the children of Israel said to them, “Oh, that we had died by the hand of the Lord in the land of Egypt, when we sat by the pots of meat and when we ate bread to the full! For you have brought us out into this wilderness to kill this whole assembly with hunger.”
4Then the Lord said to Moses, “Behold, I will rain bread from heaven for you. And the people shall go out and gather a certain quota every day, that I may test them, whether they will walk in My law or not. 5And it shall be on the sixth day that they shall prepare what they bring in, and it shall be twice as much as they gather daily.”
6Then Moses and Aaron said to all the children of Israel, “At evening you shall know that the Lord has brought you out of the land of Egypt. 7And in the morning you shall see the glory of the Lord; for He hears your complaints against the Lord. But what are we, that you complain against us?” 8Also Moses said, “This shall be seen when the Lord gives you meat to eat in the evening, and in the morning bread to the full; for the Lord hears your complaints which you make against Him. And what are we? Your complaints are not against us but against the Lord.”
9Then Moses spoke to Aaron, “Say to all the congregation of the children of Israel, ‘Come near before the Lord, for He has heard your complaints.’ ” 10Now it came to pass, as Aaron spoke to the whole congregation of the children of Israel, that they looked toward the wilderness, and behold, the glory of the Lord appeared in the cloud.
11And the Lord spoke to Moses, saying, 12“I have heard the complaints of the children of Israel. Speak to them, saying, ‘At twilight you shall eat meat, and in the morning you shall be filled with bread. And you shall know that I am the Lord your God.’ ”
13So it was that quail came up at evening and covered the camp, and in the morning the dew lay all around the camp. 14And when the layer of dew lifted, there, on the surface of the wilderness, was a small round substance, as fine as frost on the ground. 15So when the children of Israel saw it, they said to one another, “What is it?” For they did not know what it was.