Answer:
A producer is any organism that can produce its own food. The producers we know best are plants, but there's also seaweed (algae) and huge numbers of tiny sea organisms (phytoplankton).
A consumer cannot make its own food. To live, it must consume producers (plants, etc.) or other consumers (animals) or both.
Exceptions:
There are some bacteria that are producers. They can produce their own food.
There are some plants that are consumers.
Some, such as the parasite Mistletoe, consume the vital sap of other plants.
Some, such as the Venus Flytrap, consume insects, but they also produce food by photosynthesis, so they are producers AND consumers.