Is parallax a "technique to measure the star distances" or a "tiny shift in star's position"? I am not completely sure whether the Parallax is a "technique to measure the star distances" or a "tiny shift in star's position"?

The a book says two points about Parallax:


Astronomers have developed a variety of clever techniques for measuring the vast distances to stars, one is called Parallax.
Astronomers can measure a star's position once and then again 6 months later and calculate the apparent change in position. This tiny shift in stars position is called its parallax.


Apart from the book source, whatis.techtarget.com defines Parallax as the way an object’s position or direction seems to change depending on viewing angle.
It is both - a small shift of the position of a star on the sky as we see it, and a means of estimating the distance to the star.

The apparent position (with respect to very distant objects like quasars) changes because our viewing point changes as the Earth moves around the Sun in its orbit. The amount by which the position changes is inversely proportional to is distance.