Camellia Sinensis

There are five significant components found in all tea from the plant Camellia Sinensis:

Essential Oils: which are the source of tea’s delicious flavor and aroma; 

Polyphenols: which are antioxidants that provide the tea’s brisk flavor and many of its potential health benefits; 

Phytonutrients: which are small amounts of vitamins, minerals, and amino acids including L-theanine (a very rare molecule that has been found in only three sources including Camellia Sinensis); 

Enzymes: which are biological catalysts, mainly proteins generated by an organism to speed up chemical reactions to keep the body alive; 

Methylxanthines: which are a family of alkaloids that include caffeine. 
Each of these components work differently in the human body and a full description is best left to a medical journal. However, recent research exploring the potential health attributes of tea is leading many scientists to agree that tea, both green and black, may contribute positively to a healthy lifestyle.