difference between goods and resource?

In my expert campagne with the italian, I noticed that I cannot build a trading post in Corsica an Sardaigna, is it because there is no goods to trade? Resource are not tradeable?What's the difference between resource and goods to trade ?

resources are directly exploited : iron fot the weaponsmith, other resources as valuable minerals. Goods are sold; no goods, no trading posts.

Thanks for your answer el_slapper
Another question came to my mind, how do you create comercial trade with other country, is it automatic?, or do you only trade with your own province?

To trade with another faction you need an unbroken line of ships(at least one ship per sea area) from your port with the trade goods to another faction's sea coast province that also must have a port. There are no land based trade routes between factions. Any landlocked province with a tradeable commodity, only generates trade within it's own province (not a very lucrative amount unfortunately).

Intially, with just one province and a few ships, trade may not seem worth it, and will probably not even pay for the upkeep of the ships. But, as you increase the length your trade routes the amount of money you make from each trading post will go up exponentially.

What you want to aim for is to have all of your coastal provinces equipped with ports and trading posts, and to eventually have a ship in EVERY SEA LOCATION ON THE MAP. The amount of money you will make is staggering.