Tea (Camellia sinensis) is divided based on the technology/manufacture in different types, such as green, white, yellow, oolong, black, and dark tea. Matcha is a special type of green tea. Internationally agreed definitions as ISO standards are in place for green and black teas, and recently for oolong tea, while this is currently not the case for othser types of tea. International analytical standards have been issued for catechins (flavan-3-ols), theanine (amino acid), and theaflavins (condensation products of flavan-3-ols during the enzymatic oxidation). Methods for the determination of methylxanthines, such as caffeine and theobromine, are around. For other relevant groups of constituents, analytical methods have been published but no standard methods are available. New approaches, such as non-targeted metabolomics employing, e.g., UHPLC-qTOF-MS, came up since a few years. Those will become even more important in the future. Gaps in our knowledge still exist with the oxidation products despite the fact that some good hypotheses have been published for thearubigins (TR). In case of theabrownins (TBr), formed during the microbial fermentation of black tea, not much information is available. For both TRs and TBrs no convincing concept for quantification is in place. Aspects of authenticity are numerous, such as differentiation of the types of tea, the geographic origin, the age of tea, among others. A number of approaches have been published for that purpose using a variety of methods; however, no common agreed procedures have been established. There was a progress in the last decade as regards the tools for authentication. New compounds, such as flavoalkaloids including EPSFs (N-ethyl-2-pyrrolidinone-substituted flavan-3-ols), have been identified in different types of tea and those might help to authenticate, e.g., the age of white teas. N-ethyl-2-pyrrolidinone-substituted theaflavins are specific storage markers recently identified for black teas.