When you make Food you also make `raw material` (you can also buy raw material on the market pretty cheap if you dont make your own food.
When you have raw material *and* built industry you will make Consumer Goods... Miners are really the only race thats very good at making them.
Using Goods:
You sell goods to your population for 5 credits a turn, the higher demand for goods your people have the more you can make this way. You can either make goods for your people or buy them on the market (usually going for the server max price of 4).
Depending on which server you are playing on you can make a good deal of money as a goods miner.
simple words, have 50 agriculture, have 50 industry, on your planets if your a uber new dude, when you get like more clusters and have alot of money start to buy from market.
Industry is how you make consumer goods but, as Blazed said, you also need raw material, which can either be produced as a by-product of agriculture, or just bought from the market =]