Regarding the demand, anything your colony needs is imported. That is, mercantile convoys from other factions will bring goods that your colony needs from other colonies over. For food, organics, goods and supplies, this is handled by the aforementioned mercantile convoys. However, for drugs, as they are illegal goods in most factions, their trade is handled by Smugglers instead(they always fly dark around stations, you can see they occasionally in the core).
TLDR: Demand is not something you need to worry about until you start *** off factions. However, if you want to fill in your demand from in-faction imports rather than rely on other factions:
Food is produced by Farming. This needs a habitable world(not your colony, which is volcanic) to produce food.
Supplies are produced by Heavy Industry. This can be built anywhere, but preferably on a non-habitable world due to reasons you will find out later.
Goods(Domestic, Luxury) are created by Light Industry. This can be built anywhere. Also, if you enable Free Port(IE hegemony/luddic bait), it also creates and exports drugs.
Organics are produced by Mining, BUT only if the planet has some sort of Organics production modifier on it. This modifier is usually only found on habitable worlds, though I do believe some other types can have it rarely.
Also, tip: When your colony gets to size 4, get a Refining built. Not only is it insanely profitable, the demand should be completely fulfilled by your Mining. I wouldn't quite suggest putting in things like battlestations or heavy batteries because they cost a lot and at this current state, nothing should threaten your colony except pirate raids, and said raids should be extremely easy kills.
Also, Storage is your personal storage. Nobody takes things from there except you, for obvious reasons(privacy you know). Stockpiles are basically where excesses from what you produce are stored. Everything you can export is stored in excess there, and even some you don't export with the right structure(Waystation). These items usually just sit there, they are actually meant to combat shortages. Shortages only occur if your colony is raided or shipping disruptions occur. Demand is NOT necessarily a shortage, as by default demand is always met by imports. When a shortage occurs, you can click a button above the column that shows your exports/demands (use stockpiles during shortages) which will let you combat shortages at a monthly price for taking things from storage(idk either man).
If you have a shortage, there will be a red outline of the shortaged good next to the normal symbols.