Manna according to the Bible, was eaten by the Israelites during their 40 years travels in the desert, but it then ceased to appear once they had reached Canaan.

In the Book of Exodus, manna is described as appearing each morning after the dew had gone, comparable to hoarfrost in size,  and so also had to be collected before it was melted by the heat of the sun.  

It is described as resembling coriander seed, white in colour.  According to the Book of Numbers, the Israelites ground it up and pounded it into cakes, which were then baked, resulting in something that tasted like olive oil;  the Book of Exodus states that it tasted like wafers that had been made with honey. Talmudic scholars argues instead that the differences in description were due to the taste varying depending on who ate it, with it tasting like honey for small children, like bread for youths, and like oil for the elderly.

According to the biblical text, each day manna was gathered per member of each household,  regardless of how much effort was put into gathering it - some people were diligent enough to go into the fields to gather it whereas lazy individuals just lay down and caught it with their outstretched hands.  Nevertheless, according to the Talmud, manna was found near to the homes of those with strong belief in, and far from the homes of those with doubts.

Hard to swallow or rather...

As a natural food substance, the consumption of manna would produce waste products; but in classical rabbinical literature, as a supernatural substance, it was argued that manna produced no waste, resulting in no defecation among the Israelites until several decades later, when the manna had ceased to fall. According to modern medical science, the lack of defecation over such a long period of time would cause extremely severe bowel problems, especially when other food later began to be consumed again; the classical rabbinical writers argue that the Israelites complained about the lack of defecation, and were concerned about potential bowel problems.

Later cultural references

By extension "manna" has been used to refer to any divine or spiritual nourishment. Manna also means ‘mother’ in Greek and ‘where’ in Malay.

So in conclusion... Mum’s food is always the best. And where does one get this food from heaven when mum's not around? Manna of course!