Mutualistic association between fungi and algae is called
Lichen represents stable mutualistic consortium between mycobiont, usually Ascomycota comprising 98% lichens, and photobiont: green alga such as Trebouxia or cyanobacterium such as Nostoc fixing nitrogen. Fungus provides thallus structure, water retention, UV protection and mineral scavenging, algae performs photosynthesis sharing carbohydrates as ribitol or glucose. Resulting thallus forms crustose, foliose or fruticose morphologies colonizing extreme habitats serving as bioindicators of air quality and pioneers. Mycorrhiza involves fungi and plant roots, Rhizobia are bacterial nodule symbionts, endophyte lives inside plant without distinct macroscopic composite organism.
Ref: Campbell Biology 12th ed., Chapter 31: Lichens Mutualism Algae Fungi; NCERT Class 11 Biology - Lichen Symbiosis; NCBI Lichen Biology