The microorganism you are describing is most likely a one-celled organism called Euglena. Euglena is like an animal, in that it moves around by means of a single, whip-like flagellum, which rows back and forth like a paddle moving a boat. Euglena is also uniq:ue in that it possesses chloroplasts, like a plant. The chloroplasts allow the Euglena to make it's own food, using sunlight in a process called photosynthesis. The formula for photosynthesis is shown below:
CO2 + H2O (subscripts) + sunlight ---> C6H12O6 + O2 (subscripts)
The Euglena falls into an interesting position in taxonomy, as it possesses both qualities that generally define animal cells or plant cells. As such, it is either an animal that can manufacture it's own food, or a plant that can move around.