I hear/ read different meanings and see videos of people being Alpha. But, what is it at the very core?

I've read so much on what a Alpha should be or is and its confusing. "Alpha should be confident, a leader etc…" Yet I still find the term Alpha being used in cases many many other cases. Because it seems everyone has a different idea of what a Alpha male is...

So my question is What is it to be Alpha at its very core?