What Is Tea? Understanding Camellia Sinensis, Tea Types, and Oxidation

Although many hot beverages prepared with water are commonly called “tea,” true tea is defined more specifically. Technically speaking, a drink is only considered tea if it is made from the leaves of the Camellia sinensis plant. This evergreen plant originated in China and India, where tea has been cultivated, brewed, and enjoyed for thousands of years.

Today, Camellia sinensis tea is grown across the globe—from Japan and Taiwan to Sri Lanka, Kenya, and even parts of England—making tea one of the most internationally beloved beverages in the world.

One Plant, Many Teas

It may surprise some tea drinkers to learn that green tea, white tea, black tea, oolong tea, and pu’erh tea are all produced from the same plant. The remarkable diversity of tea flavors, aromas, and colors does not come from different plants, but rather from:

• Terroir (climate, soil, altitude, and environment)

• Tea cultivar (there are two main Camellia sinensis varieties, plus regional cultivars)

• Processing methods after harvest

Much like wine grapes, tea leaves express their environment. However, what ultimately determines whether a tea becomes green, oolong, black, or pu’erh is how the leaves are processed.

The Role of Oxidation in Tea Processing

The key factor that differentiates tea types is oxidation—a natural chemical reaction that begins the moment tea leaves are plucked from the plant. As the leaves are exposed to air, enzymes interact with oxygen, changing the leaf’s structure, flavor, and color.

Here’s how tea types fall along the oxidation spectrum:

• White Tea – Minimally processed and the least oxidized. White tea retains its silvery buds and delicate flavor, producing a light, soft liquor.

• Green Tea – Lightly oxidized or not oxidized at all. Heat is applied early to stop oxidation, preserving fresh, vegetal flavors.

• Oolong Tea – Partially oxidized. Oolongs span a wide range of styles, from floral and creamy to roasted and robust.

• Black Tea – Fully oxidized. The leaves darken completely, resulting in a bold flavor and deep amber or reddish liquor.

• Pu’erh Tea – Both oxidized and fermented, undergoing microbial aging that deepens flavor over time. Pu’erh often improves with age, much like fine wine.

Why Tea Matters: Health and Global Popularity

Tea is the second most consumed beverage in the world after water, and its popularity continues to rise—especially in North America. Increased research into tea’s health benefits has drawn attention to its rich content of antioxidants, polyphenols, and amino acids.

Regular tea consumption has been linked to:

• Improved cardiovascular health

• Support for weight management

• Reduced inflammation

• Protection against oxidative stress

• Enhanced focus and calm energy

Tea is also naturally calorie-free, sugar-free, gluten-free, fat-free, and preservative-free. While tea does contain caffeine, it delivers a smoother energy boost thanks to L-theanine, an amino acid that promotes relaxation and mental clarity—without the jitters commonly associated with coffee.

Tea vs. Tisanes: What’s the Difference?

Strictly speaking, only beverages made from Camellia sinensis qualify as true tea. Drinks made from herbs, flowers, fruits, roots, or spices—such as chamomile, peppermint, rooibos, or ginger—are more accurately called tisanes or herbal infusions.

For simplicity and common usage, we’ll continue to use the broader term “tea” while clearly distinguishing:

• Leaf teas (from Camellia sinensis)

• Herbal, floral, fruit, or root infusions (non-tea plants)

That distinction helps keep things clear—while still letting everyone enjoy their favorite cup