The names tangerine and clementine are generic and interchangeable. In fact the original Clementine variety was called an Algerian Tangerine. I've studied this quite intensively.
Like apples or potatoes, there are many different varieties, some more commonly available than others
Most varieties are hybrids of various fruits.
Nadorcotts, clemenules, tangos, novas all have different characteristics and are different depending where they are grown and when they are picked. They each have a short season so are available at different times of the year. Personally, I find the Spanish and South African grown fruit better than the South American or Australian ones.
But look at the labels, they always have the variety on, and if you find one you like, maybe try a different one next time.