The simple answer is that a Kohane is a male descendant of Aaron, the older brother of Moses. Here’s a little more info…
The Hebrew word “kohane” is usually translated as “priest.” Invariably the usage of the word in the Jewish Bible suggests a high level of attachment to God, and also suggests special qualification for helping and serving others. The term priest/kohane is not exclusive to Jewish people, as is clear in the Biblical mention of Melchitzedek, who in the 14th chapter of “Genesis” blesses Avraham (still named Avram at that time in the narrative).
Later, when the Jewish people are formed into a post-exodus society, some specific duties of communal religious observance are assigned to Aaron, the older brother of Moses, and to the sons of Aaron. The assignment of these duties is ordained by God – a point that is strengthened when the priestly authority is questioned by a cousin. (Writer’s note: yes, I know this is a diversion from the main point of the page, but I feel compelled to point out the very human nature of the Biblical characters).
The ritual responsibilities and authority of Aaron are reflected in the term “Kohane,” which is also used for his sons. Later the term is applied to Aaron’s grandson, Pinchas (sometimes written in English as Phineas), and to the descendants of Pinchas in perpetuity.
The list of duties and rituals assigned to Aaron and his descendants is not a complete list of Biblical duties. In fact, the Bible has duties for every person. Every man. Every woman. Every child. Every person of every nation – whether royalty or commoner, and not just for Jews.
The duty of blessing the people is specific and exclusive to Aaron and his descendants.
Many of the assignments given to Kohanim carry status with them. But the Kohanim were also restricted in many of their activities, in whom they could marry, and in their ability to own land in the Promised Land. From personal experience I can state that it is not always good to be a kohane.