1. Mutualism is a type of relationship that can be seen between two individuals of two different species to obtain benefits for both of individuals.
Examples : Coral polyps and zooxanthellae
bee and flower
Lichens
Rhizobium and root nodules
Ungulates and bacteria which live in their intestines
2. Commensalism (this is the correct word) is a type of relationship between two organisms which belonged to two different species that one individual obtains benefits while other doesn't have any harm or benefit.
Examples : Remora and sharks
Orchids and trees
Pseudoscorpions and Beetles
Cattle Egrets and Livestock
hermit crab and sea anemone
3. Parasitism is a relationship between two organisms of two different species where one individual (parasite) gets benefits by harming other individual (host).
Examples : Cuscuta (parasite) and angiosperms (host)
Parasitic viruses (parasite) and human (host)
Tape worms (parasite) and pigs (host)
Flukes (parasite) and human (host)
Parasitic bacteria (parasite) and human (host)