Names of Redwood Trees
There are three species of trees that can be called "a true" Redwood tree;
The Coast Redwood (Sequoia sempervirens). Also commonly known as the California Redwood, or just "Redwood". When people are talking about Redwood trees, this is the species they are most likely thinking about. It can grow the tallest of all the Redwood trees, and also the tallest tree on Earth is a Coast Redwood.
The Giant Redwood (Sequoiadendron giganteum). Also commonly known as the Giant Sequoia, Sierra Redwood, Sierran Redwood, Wellingtonia. These trees can grow very tall, even though not the tallest, they are the largest trees, for weight and volume. The Giant Redwood trees have the widest trunks of all the Redwood trees, and of all the Gymnosperm plants on Earth.
The Dawn Redwood (Metasequoia glyptostroboides). Its the shortest of the Redwood trees, however it grows to at least 200ft (61m) tall. It is well known due to the fact that is is one of a few Deciduous Conifer trees, it sheds it's needles - leaves every Autumn.
All three species belong to monolithic genus's (Sequoia, Sequoiadendron, and Metasequoia), as the other species of each genus are extinct. All three genus's are the only members of the botanical taxonomic Subfamily Sequoioideae, commonly known as "The Redwoods".