Cilantro, or Chinese parsley, is the name given to the leaves of the coriander plant (Coriandrum sativum), while both the plant and the seed-like fruit are traditionally called coriander. This is changing, as many people who use the herb may be unaware that the plant yields another spice and refer to the entire plant as cilantro. The coriander plant is in the same family, Apiaceae, as anise, fennel, dill, caraway, and cumin.
The spice does have a very disagreeable taste to some people. Studies have been made but it's something of a mystery as to why.
Most people like it though.
Science Explains Why Cilantro Tastes Like Soap For Certain People:
http://www.huffingtonpost.com/2015/06/24/why-does-cilantro-taste-bad-like-soap_n_7653808.html