Parasitism is a relationship between two organisms in which one (parasite) benefits and the other (host) experiences harm.
Ectoparasites:
The parasites feed on the host organism's exterior surface.
Head lice are ectoparasites that feed on human blood.
Cuscuta, a parasitic plant that grows on hedge plants, has lost its chlorophyll and leaves over time. It feeds on the plant that it parasitizes for nourishment.
Endoparasites:
Endoparasites are parasites that dwell in the host body at various locations such as lungs, kidneys, and blood cells.
Their life cycles are more complicated due to their great specialization.
For example - Human malaria is caused by the endoparasite Plasmodium falciparum.