Tea culture is diverse, and there are many different largely non-overlapping traditions of tea, associated with different countries, production methods, and styles of tea preparation.
The main divides are between English and British tea culture, and the closely related European cultures, which favor strong black teas and blends like Earl Grey, and the Asian cultures which tend to focus more on green teas. Asian tea culture is further divided into Japanese green teas vs. Chinese green teas and other Chinese teas like oolong and Pu-erh. Pu-erh is really a culture of its own, appreciated mostly by a small group of connoisseurs. Different tea companies focus on teas from different countries and cultures.
There are also numerous companies that specialize in herbal teas: some of these brands specialize in medicinal teas, whereas others focus on herbal teas more as beverages. Also common are blends of tea with herbs and other flavorings, common among mainstream brands like Tazo and Bigelow. Even among brands that focus on flavored teas, there are certain flavor aesthetics that each company favors or leans towards. Learning these can help you buy what you most enjoy drinking.
If you want to buy Japanese tea, buy from a Japanese company or one with Japanese roots or expertise, not one that focuses on English teas, and vice versa if you want a British-style tea. Think of what teas you enjoy the most, and buy from a brand with a focus on those styles of tea.