(a) Parasitism: It is an interaction between two different species in which the smaller partner (parasite) obtains food from the larger partner (host or plant). So the parasitic species is benefitted while the host species is harmed. Based on the host-parasite relationship, parasitism is classified into two types they are holoparasite and hemiparasite.

(b) Holoparasites: The organisms which are dependent upon the host plants for their entire nutrition are called Holoparasites. They are also called total parasites. 

Examples:

• Cuscuta is a total stem parasite of the host plant Acacia, Duranta and many other pQlants. Cuscuta even gets flower inducing hormone from its host plant. 
• Balanophora, orobanche and Refflesia are the total root parasites found on higher plants.

(c) Hemiparasites: The organisms which derive only water and minerals from their host plant while synthesizing their own food by photosynthesis are called Hemiparasites. They are also called partial parasites.

Examples:

• Viscum and Loranthus are partial stem parasites.
• Santalum (Sandal Wood) is a partial root parasite. The parasitic plants produce the haustorial roots inside the host plant to absorb nutrients from the vascular tissues of host plants.