What is commensalism?

Commensalism is a type of population interaction in which one species benefits and the other species is neither harmed nor benefited.
In this interaction,the species that benefits is called the commensal,while the other species remains unaffected.
For example,an orchid growing as an epiphyte on the branches of a mango tree benefits by getting support and exposure to light,while the mango tree is neither harmed nor benefited by the presence of the orchid.