They are simple, unicellular eukaryotic organisms.
They are neither plants nor animals or fungi.
Mode of nutrition- autotrophs (prepare their own food), heterotrophs (obtain nutrition from other organisms), and some are decomposers (obtain nutrition from decaying matter).
Some protists are harmful. They cause disease in their hosts.
Example- Trypanosoma (causes sleeping sickness), Giardia (causes Giardiasis in the gastrointestinal tract), and Plasmodium (causes malaria).