Basically, the difference between flexography and offset printing is the machine setup.
3 different types of flexographic machines exist.

The Satellite Machine

Here is an illustration of a so-called satellite machine. It is named so as it is surrounded by all the printing heads like small satellites.
This machine is used most frequently because the paper fits tightly on the large water-cooled back-pressure cylinder.

The Stack Type Machine

Another machine is the stack type machine. Named so because the printing heads are placed on top of each other as seen below. This machine type is often used for wide format paper and flexible materials.
The down-side of this machine type is that it is difficult to access. This means that the printers have to crawl onto the machine to replace different parts.

The In-Line Machine

The in-line machine is used at Grafiket and it is a machine type most often used for label manufacturing.
The advantage of this machine is that the printing heads are placed next to each other making it easier to monitor the pressure.
Another big difference is that water-based colours are used in stead of oil-based. Many different material types may be used like plastic bags, carton or foil.