A producer is an organism which makes its own food, like a plant, any photosynthetic or chemosynthetic organism.
After a producer, anything which eats something else in the food chain for energy is called a consumer.
There are 3 types of consumers
Lets break down as food chain
Phytoplankton are microscopic Organisms capable of photosynthesis.
Producer
Primary consumer
Secondary consumer
Tertiary consumer
Krill eat the plankton
Fish eat the Krill
Penguins eat the fish
The arrows in food chains show the way in which energy is moving, not what eats what. The reason we say energy, is because we also have parasite-host food chains.
Something you might not always see in a food chain/web, but are always present in every ecosystem are decomposers.
These organisms break down complex organic matter into inorganic matter. These are extremely important parts of the ecosystem because they recycle all the dead matter back into the earth.
Fungi and bacteria are two forms of decomposers. They break down anything which is dead, from a producer to a consumer.