What is a mixotrophic nutrition and do you know an organism that feeds like that?

Mixotrophic nutrition refers to organisms which are both autotrophs and heterotrophs. A mixotroph is an organism that can use a mix of different sources of energy and carbon, instead of having a single trophic mode on the continuum from complete autotrophy at one end to heterotrophy at the other.

An organism that feeds like that is a Euglena.