By Process, we mean an activity that transforms inputs into outputs. The outputs might then become inputs to other processes, forming networks and chains. Those chains may be circular, where an output from one process becomes an input to another process that occurred previously in the same chain.
For example: a farming process takes compost, soil, seeds, water and human and mechanical work as inputs, and transforms them into grains, nuts, fruit, and vegetables. Those ingredients may go to kitchens that create dinners for people to eat. Some of those ingredients may be pared off in preparation, or spoil, or be left on plates. Those leftovers go into compost, which starts the process chain over from the beginning.
Or for a bad example: a CAFO (Confined Animal Feeding Operation) produces a lot of manure. They put manure into big lagoons, which drain into the water table, and come back up in people's drinking water, causing diseases, for which the people become inputs to a hospital.
One of the inputs to the CAFO process is antibiotics. The animals are filled with antibiotics because they get sick in the CAFO environment. And the antibiotics are also an output, mixed in with the manure.
The antibiotics then breed resistant bacteria, which end up in the people, and send them to the hospital, and then kill the people, because the common antibiotics no longer work. And the resistant bacteria remain in the hospital to kill other people.
Connected processes enable us to see cause and effect, if we want.
Below is a view of processes, which occur in resource flow networks, and live in three layers: Abstract, which describe how processes work. Plans, which describe processes which are intended to happen. And Observation, which is a record of processes that have already happened.
Here is a specific example: