A group of six fruited Rangpur lime trees has special importance in Hindu culture. Perhaps my favorite tradition involving citrus is the significance of the Etrog citron in Judaic culture. When I grew Etrog citron trees a few years ago, I learned that the trees must grow on their own roots, either from seed or cuttings. Fruit from grafted trees would not be kosher. The most popular of citrus include sweet orange, lemon, lime, grapefruit and mandarin orange.
Tangerines are actually the same as mandarin oranges, but have been developed in California.
The variations of the more common citrus are distinguished by their acid content or flavor. For example, sweet oranges are what most people are familiar with for eating fresh, or juicing. Variations include sour oranges and bitter oranges. The fruit of sour orange trees are used in marmalades. Bitter orange fruit is used in flavor extracts, fragrances and furniture polish.