The papaya originates from Central and South America and there are a few different varieties. Most of the commercially available papayas are long and cylindrical, but there are rounder shorter ones, as well as a really interesting variety I recently found growing on Dieng Plateau in Java Indonesia. It's a local specialty there.
Papaya can be eaten unripe - the most famous recipe being Som Tam, or green papaya salad, which is a favourite of mine. Nice and spicy! You can also add green papaya to a roast or stew and it will tenderise the meat due to the papain in it (an enzyme which breaks down protein).
Mostly papaya is eaten when it's ripe and golden yellow, usually with a splash of lime juice over it to bring out the sweetness.
It also makes a pretty yummy fruit smoothy!
The papaya plant is really easy to grow and easily germinated from seed collected from a store bought fruit. It's a tall single stemmed plant, which produces leaves which can be lightly steamed and eaten. They can be quite bitter, so only use very young leaves. They produce fruit straight off the main trunk, but only if they aren't males!
The papaya plant can be male, female or bisexual. Usually the ones sold in garden centres are bisexual, meaning the fertilisation happens within each flower, but I frequently save my papaya seeds from bought fruit and sow them, meaning I sometimes end up with papayas of either sex.
You only need one male to fertilise about 7 females, but they are quite pretty in their own right. Lots of clusters of white flowers, with a gentle perfume.
The females flower and then produce fruit at the flower's base if fertilised. The bisexuals self mate so they tend to start fruiting quicker.
So grab the seeds out of your next papaya and sow them and see what you get.
They like a bit of water and nutrients, but they don't like wet feet or they'll rot. They're a lovely addition to a garden that doesn't get frosts (though those Dieng papayas are at high altitude so there may be hope for you cold climate gardeners after all)