Some basic definitions on algebraic geometry

Question

I have a question on some definitions in algebraic geometry.

I just started to read the book Field Arithmetic, by M.Fried and M.Jarden, but I cannot find the definitions they use.

Fix $K$ a field. What is a absolutely irreducible variety over $K$? What is a $K$-rational point of a variety?

Do you have a reference where i can read about these definitions?

Thanks!

Answer 1

An absolutely irreducible variety is a variety which is irreducible over an algebraically closed extension of $K$.

A $K$-rational points is just a point of the variety with coordinates in $K$.