Cargo is one of the two things that can be delivered as jobs in Pocket Planes. The other thing you can deliver are Passengers. In the game, there are two types of cargo: normal cargo and rare cargo.
Normal cargo is the more common cargo. Each cargo is randomly given an image and name. According to a tweet from the game developer, there are 400 types of cargo that can be generated in the game. (You can view this tweet here) The payment in coins you recieve for delivering the cargo is determined by how far away the origin and the destination of the cargo is - the actual formula is $ Payment = Distance + 50 $, where the distance is in miles (rather than the range of the plane).
The other type of Cargo in Pocket Planes is rare cargo. Instead of having generic cargo images like normal cargo, rare cargo each has their own specific image. Rare cargo is usually expensive or fragile, like a 1st Place Orchid. Instead of being rewarded with coins, for delivering rare cargo you get rewarded with Bux. Below are the rare cargo that you can deliver in the game, along with the image associated with the item.
NOTE: Not all of the rare cargo items have been posted yet. Known items in need of images: Flight Log (indicates an image is being processed)
Event cargo is used for events. The images are the same as rare cargo, but have different names.