Protists can be plant-like, animal-like, or fungus-like and they are the most diverse group of organisms.
Think back to the six kingdoms (see image) and remember that Bacteria and Archaea are prokaryotes. The other four kingdoms are eukaryotes, including Protista.
Remember that eukaryotes all have a distinct nucleus, bound by a membrane and other membrane bound cell organelles. Most protists are single cell, however a few are multicellular.
Take the time to watch the Brightstorm video, Protist Kingdom, before moving on.