Fungi and Algae are both considered plantlike, but lack certain characteristics of plants.
Fungi are plantlike organisms that cannot produce their own food. Fungi survive by leaching energy from organisms that are either alive, or dead. Fungi are important for breaking down dead organisms into material that can be used by plants.
Algae are organisms that can produce their own food through photosynthesis. Algae can only live in aquatic environments because they lack roots and stems required for stability on land. Much of the earth's oxygen is produced by algae.
When fungi and algae live together in a mutual relationship, they are known as lichen. Lichen are fungus that have algae cells living among them. The two depend on each other. Fungus provide food for the algae, and algae are able to live in environments that they normally wouldn't be able to.